Baker Bettie

The Science of The Chocolate Chip Cookie

Learn chocolate chip cookie science so you can create your perfect cookie! Love a really chewy cookie? Or a really crispy cookie? OR how about cakey? These guidelines will help you edit your cookie recipes to create your own perfect chocolate chip cookie! 

There is no doubt in my mind that Chocolate Chip Cookies are the ultimate classic baked good and comfort food.  There is just nothing that compares to a warm gooey cookie right out of the oven. And in my early baking years I set out on a mission to develop the most perfect chocolate chip cookie recipe ever.

But this led to the question: What is my idea of the perfect chocolate chip cookie? I am all about contrasts, so I want a variety of textures and flavors. So I worked hard to create that for myself. A thick, chewy on the inside crunchy on the outside cookie that has hints of caramel and salt with dark chocolate chips and toasted pecans. You can find my Ultimate Chocolate Chip Cookie Recipe here.

But this process of creating my own perfect chocolate chip cookie showed me that not everyone has the same idea of what makes a chocolate chip cookie truly perfect. You might like yours super thin and chewy. Or maybe really thick and cakey. So I am here to teach you the chocolate chip cookie science so that you might create your own perfect cookie.

The Basic Chocolate Chip Cookie

Let’s start at the beginning with the Nestle Toll House Cookie Recipe. You know, the one on the back of the bag of chocolate chips? It’s the standard, classic Chocolate Chip Cookie Recipe.

It creates a fairly middle road cookie. Chewy in the middle, slightly crispy on the edges, with a fairly one note flavor profile. These are the nostalgic cookies from my childhood.

Nestle Toll House Cookie Recipe

  • 2 1/4 cups all-purpose flour
  • 1 tsp baking soda
  • 1 tsp salt
  • 1 cup butter, softened
  • 3/4 cup granulated sugar
  • 3/4 cup packed brown sugar
  • 1 tsp vanilla
  • 2 large eggs
  • 2 cups Nestle Toll House Chocolate Chips
  • 2 1/4 cups all-purpose flour
You know the drill: Combine dry ingredients.  Cream butter and sugar.  Add the other wet ingredients.  Add the dry ingredients to the wet and the chips.  Bake in a 375 degree oven for 9-11 minutes.

Changing the Ingredients to Achieve Your Desired Texture

I see the Toll House recipe as a fairly neutral chocolate chip cookie recipe and a good starting point for manipulation to create your own perfect cookie. Each ingredient of this recipe can be altered to change the final product based your own preferences. Let’s review each ingredient.


  • If you want chewier cookies change out the all-purpose flour for bread flour.  Bread flour has more protein and therefore will create more gluten.
  • If you want cakier cookies increase the amount of flour to 2 1/2 cups.
  • If you want thicker cookies with lots of texture cut back the flour to 2 cups and add 1 cup of oat flour.  You can find this in the grocery store or create your own by grinding old fashioned oats in a blender to a fine crumb.

Baking Soda & Baking Powder

  • If you want cakier cookies, add 1 tsp of baking powder and keep the 1 tsp of baking soda.
  • If you want flatter cookies, eliminate the baking soda from the recipe.


Salt is one of the ingredients that only affects the flavor.  You can reduce or increase this amount according to your own preference for the salty/sweet combo.  But don’t eliminate it completely! I usually increase it to 1 1/4 tsp and use Morton kosher salt for a more coarse flake.


  •  If you are wanting a nice chew to your cookies and have decided to opt for the bread flour, melt the butter.  The water from the melted butter will mix with the flour to create more gluten.
  • If you like a more complex caramel flavor to your cookies, brown the butter 
  • If you want taller, cakey cookies, use shortening instead of butter or half shortening half butter.  You can use butter flavored shortening if you want to keep the butter taste, but some people prefer the flavor of regular shortening.
  • If you want a very soft cookie, replace all or some of the butter with shortening.


The ratios of the white sugar to brown sugar are important to produce the kind of cookie you want.

Higher white sugar to brown sugar ratios will produce a more crisp and crunchy cookie while higher brown sugar to white sugar ratios will produce a more soft and chewy cookie.

Dark brown sugar will up the chewiness even more.  Play around with it to produce the texture you want!


 Vanilla only affects the flavor of your chocolate chip cookies.  Increase the amount up to 1 tbsp if you really like the flavor, or eliminate all together if you want a more buttery flavor.  You can also use Mexican vanilla for a more unique flavor.  It almost has hints of cinnamon.


  • If you want a flatter cookie, eliminate 1 egg and cut back the flour to 2 cups
  • If you like a really crunchy cookie, add another egg white because it helps to dry out baked goods.
  • If you prefer a moist and chewy cookie, eliminate one egg white and add 2 TBSP of milk.


And now that you have your perfect cookie texture, add-ins are where you get to let your creativity go! Are you a milk chocolate or a dark chocolate person? Or maybe you even want white chocolate chips or a combo of different kinds! You could also add spices or zests or extracts. Or how about dried fruit or toasted coconut or nuts? There are literally endless possibilities!

Other Variables that Effect Texture


  • If you want a thicker cookie that doesn’t spread as much, bake them at a higher temperature (375F) for a shorter time and chill the dough prior to baking. This will allow the outside of the cookie to set before the butter and sugar melt and spread.
  • If you want really flat cookies, bake at a lower temperature (325F) to allow the sugar and butter to melt before the cookie sets.

Baking Time

  • If you want really soft cookies, pull them from the oven with the middles still look underdone.
  • If you want really crispy cookies, allow them to cook longer until the cookie looks fully cooked through and allow them to cool completely on the baking sheet.

Other Tips

  • Always bake your cookies in small batches to produce even browning.  (I cook 6 at a time)
  • Use a cookie scoop for perfectly shaped cookies & add a few chips to the tops of each dough mound before going into the oven for that perfect chocolate chip cookie look.
  • Larger cookies tend to bake more evenly.
  • Make sure you are using the spoon and level method of measuring your flour so you don’t end up with too much in your cookie dough!


Chocolate Chip Cookie Recipes you Might Enjoy

Using the rules as stated above I have made various cookie recipes over the years with a variety of textures. Below you will find my recipe for Perfect Thin & Chewy Chocolate Chip Cookies. If you are looking for a different texture, check out one of my other cookie recipes or try creating your own!

Thin and Chewy Chocolate Chip Cookies

Thin and Chewy Chocolate Chip Cookies

Yield: 2 Dozen Cookies
Prep Time: 1 hour 10 minutes
Cook Time: 14 minutes

This recipe creates the perfect thin and chewy chocolate chip cookie.


  • 2 1/4 cups bread flour
  • 1 tsp baking soda
  • 1 1/4 tsp kosher salt
  • 2 sticks unsalted butter, melted
  • 1/4 cup granulated sugar
  • 1 1/2 cup dark brown sugar
  • 1 egg
  • 2 tbsp milk
  • 1 tbsp vanilla
  • 2 cups chocolate chips


  1. Melt the butter and allow to cool slightly.
  2. In a small bowl, whisk together the bread flour, baking soda, and salt in a medium bowl.
  3. Add the melted butter to the bowl of a stand mixer fitted with a paddle attachment. Beat the butter, granulated sugar, and dark brown sugar until combined.
  4. Add the egg, milk and the vanilla and beat on medium slow speed until incorporated.
  5. With the mixer on low speed, gradually add the dry ingredients into the wet ingredients until just incorporated. Scrape down the bowl as needed. Add in the chocolate chips and mix until incorporated.
  6. Allow the dough to rest for 1 hour in the refrigerator.
  7. Preheat the oven to 350 degrees. Line baking sheets with foil or parchment paper.
  8. Using a large scoop, drop 6 dough balls onto each cookie sheet.
  9. Bake for 11-14 minutes at 350F, just until the edges are lightly browned.
  10. Slide the cookies on the foil or parchment off the cookies sheet as soon as they come out of the oven.


Note: The cookies will be just slightly crunchy on the edges when cooled. If you want a completely chewy cookie and can resist eating them right away, store in an airtight container overnight and the cookies will be very chewy and soft in the morning.

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209 comments on “The Science of The Chocolate Chip Cookie”

  1. OH….

    These are the cookies of my dreams I had been waiting for. A light crunch, chewy but not too much so. These are heaven. But I guess heaven comes at a price. This recipe made about 18 cookies. 2 sticks of butter divided by 18 cookies is… a mess of a lot of butter per cookie. I had to give a dozen away, else I would have eaten them all. But seriously. This recipe can win awards.

  2. These cookies are AMAZING! I made them yesterday and found that they were the best chocolate chip cookies I ever made! I am saving this recipe!

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  5. I make the best chocolate chip cookies that anyone I’ve fed them to has tasted, but mostly what I mess with is the flavorings, not the flour, sugar, etc. I use the standard joy of cooking chocolate chip cookie recipe with the following alterations:

    add ~1 tsp of cinnamon
    replace 1 1/2 tsp vanilla with 1 tsp vanilla and 1/2 tsp almond extract
    use AT LEAST 2 cups of chocolate chips

    It’s really simple but the results are amazing.

  6. …I followed your Thin and Chewy Chocolate Chips recipe to the letter (..with the exception of using margarine instead of butter, and 2 1/2 tsp baking powder instead of baking soda (..according to your ""..) and they did not flatten at all and sort of burned on the bottom..!! I am perplexed. 🙁 I thought I had finally found the perfect 'flat and chewy' cookie. I will have to try again, and follow exactly… But would margarine instead of butter, or powder instead of soda change it that much..?? ..Or, make it not change.. They looked exactly like how I put them in! Still tastes SO GOOD, but I want them flat..!! ..Ideas..??

    • Yes! These changes would change it a lot actually! Margarine has a higher melting point than butter. When the butter melts it helps the cookie spread. With margarine the cookie will likely set before it has a chance to spread. Margarine also typically has less fat content than butter and this could lead to the burning. It is also possible that your oven is cooking too hot, which is a common problem. You could try turning it down 25ºF and see if that helps. Are you using a baking sheet that has a dark coating? That could also lead to problems.

      The substitution for the baking powder and baking soda information I posted in that post is really meant for a pinch situation. If you are wanting specific results you really can’t substitute the two. They are very different things. Substituting or leaving out will always change the results.

      My idea really is just to try the recipe as written. And possibly turning down your oven temp.

  7. Love this blog. Makes baking so interesting and fun. This chocolate chip recipe is the best ever, perfect every time. One thing I do is to use coconut palm sugar to replace the white and brown sugars. I use the same total amount and the cookies are still perfect every time. Thanks for this wonderful, fun blog.

  8. Love love love them! ! I have been tring a lot of recipes about 10.. befor I found this one just what I wanted thanks a lot 8)

  9. Seems like no matter what I try. My cookies end up puffing up in the oven instead of melting flat. I want flat cookies! Not these little mounds. I followed this to the T too.

  10. okay I have 2 Q.
    1. you said to let it rest for an 1 hour. do I let if rest in the fridge or outside? and if i let it rest in the fridge do I let it warm when i take it out?
    2. how may cookies dose it make?

    • The dough should rest in the refrigerator and no, you do not need to let it come to room temp. The chilled dough will bake more evenly. It really depends on how big you make your cookies, but this should yield 2 dozen large cookies or 4 dozen small cookies.

  11. This could be an elevation issue. Do you live at a high elevation? This could also be too much flour in your batter. How do you measure your flour? You want to fluff it up with a spoon or fork and very lightly spoon it into the measuring cups without packing it down. Then level it off with a knife. If you have a kitchen scale, that would even more more accurate. 1 cup of flour should weigh 4.5 oz. So for this recipe you need 10.1oz. Also, are you making sure to cream your butter and sugar well? I will edit the recipe to reflect this, but you want to cream it together for about a minute. The little bit of air incorporated into the batter here will help it spread. Hopefully this helps!

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  13. These cookies turned out absolutely perfect! I've been trying out more recipes than I can count, and this one gave by far the best results. The dough did turn out quite liquidy but it hardened to a nice consistency after I refrigerated it for a while.

  14. I made these today and they were ok. They didn’t really flatten out (even though I followed the recipe) so I flattened them out myself. Taste wise they were kinda bland, almost like something was missing but the texture was nice. I think that next time when I make these I’ll add more vanilla and maybe some spices like cinnamon but overall these were ok.

  15. These cookies are fabulous right out of the oven! However, mine hardened a little more than I like by the next morning. Any idea as to why?

    • How did you store the cookies Heather? They are best stored in an airtight container. It will trap the moisture in and keep them soft. It also sounds like the cookies may have been a bit over baked.

  16. Hi! How many gramms in one stick of butter?

  17. I found that flattening the batter before baking yielded flatter cookies than just leaving the batter in mounds. I like my cookies flat not cakey, crispy edges, chewy centre, caramel flavour with a hint of salt. 🙂

  18. I was wondering after I placed them on the sheet if I could just leave them in the fridge overnight so I can bake them in the morning?

  19. I was wondering after I placed them on the sheet if I could just leave them in the fridge overnight so I can bake them in the morning?

  20. Hi, is it safe to use parchment paper to separate cookies when storing them? Thanks

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  25. Betty, you ROCK!

    I’ve been searching what seems like all my life for these perfect cookies. Thanks for all your work.


  26. Hello!

    I am excited to try this recipe! I’ve tried many recipes to no avail; I’m hoping the bread flour is the trick that does it.
    What if I wanted to keep the thin and chewy aspects, but make it a thin, chewy, chocolate chip oatmeal cookie? Would I need a totally new recipe or would I just adjust the flour and add some oatmeal?

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  28. I don’t know what I did wrong, but the chocolate chip cookies didn’t turn out, at all. I refrigerated the dough for two hours and when I put them in the oven, they spread out into the entire pan, with the chocolate chips piled up in the center of each spot I dropped the dough onto. When cooled, I lifted the mess off the parchment, and it’s so buttery/greasy that you can’t eat them.
    I tried a pan with the oven temperature at 375 instead of 350, and reduced bake time, and same problem. Where did I go wrong?

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  30. if I am making the flat and chewy recipe above, could I use light brown sugar with them still staying flat?

  31. Hi! What bugs me often is how can I “safely” chill or let rest any dough that has baking soda in it, be it for cookies or cake. Because unlike baking powder, which reacts to temperature, baking soda reacts to acidic ingredients and we should rush to put in the oven whatever we’ve just concocted with baking soda, so we don’t “lose” its power . Isn’t that the idea? And yet often, we’re asked to refrigerate the dough… This idea often stands in my way of making cake, because I only have one cake tin, and don’t want to mix the dough twice, but I’d want to just let half of it wait till the first layer finishes baking. But then I end up not making cake for that reason.. Or am I being unnecessarily careful? What are your thoughts on this very important matter? 🙂
    I think it’s cool that you’re interested in the science of baking! It’s fascinating to me too. I wanna know more about it especially for the purpose of being able to do adaptations and substitutions to recipes to make them healthier, but without messing it up, as it sometimes happens :)…

    • Hi there Tea,

      You are correct, baking soda does immediately start reacting creating C02 once it is hydrated, however, baking soda in most cookie recipes really isn’t for the purposes of leavening much. It actually serves more of the purpose of browning for the cookie. The egg as well as steam releasing from moisture evaporating does most of the leavening actually, and if baking powder is present, then it also contributes. Let me ponder/research this more and come up with a more in depth answer for you. I want to start doing some baking science question posts this year so this can be a good one to start with!

      • Wow, I had no idea the b. soda isn’t there in cookies (primarily) to leaven! So I’m guessing that’s still a no-no on chilling half the cake batter while the first layer is in the oven?
        It would be so interesting to pick your brain sometimes! You’re like an encyclopedia! I’ve only recently become interested in baking myself, and quickly became fascinated by the fact that I can manipulate certain ingredients to change the outcome. It can be such a challenge to know what you did wrong when you’re trying to ‘healthify’ goodies(because all the ‘unwanted’ ingredients play such important roles)… But the successes (inbetween some disasters) make it feel worthwhile.

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  33. I love ❤ this recipe and have used it 20 times. Only change, no bread flour, only because I usually don’t have any on hand. Thank you for the post!
    Perfect cookies every time.

  34. this is what ive been looking for !
    thanx alot bettie

    my question is ,what if i want to use whole wheat flour ?? how to substitute it , i want it to be totally whole wheat flour but i know how stony hard and dense it will turn out !
    what is the other ingredient to modify when using this flour for cookies ?? as i want to make oat whole wheat chocolate chips cookies , i really love and enjoy these nutty and oaty flovors <3

    thanx in advance !

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  36. Mine turned out thicker. I followed the recipe to. “T” . I made this recipe many times before and had great success. Not sure why this time they turned out fluffy. I still give it 5 stars as I have made it many times before this mess up and they turned out great.

  37. Love your recipe BUT if you want a yummy twist add chopped up candy bars etc. I live overseas and could not find chocolate chips for a few months. A local company here makes 1 kilo bars of milk and dark chocolate . I bought those chopped them into chunks plus I will add milk chocolate Galaxy bars. I never use chips anymore, MUCH cheaper than chocolate chips too. 

  38. Hi! I followed the recipe and got the results that I wanted – chewy on the centre, crisp on the edge. But the next day, the cookies were crumbly! Help! What could have happened?

    • Hi Joyce! How did you store them? I have a feeling that may be part of the problem. The best way to store chocolate chip cookies is to put them in an airtight container to trap the moisture in. This will likely the soften the crispy edges that you wanted though. I suggest if you are really looking for that texture specifically and they won’t be eaten within the day, possibly only bake what you and your family will eat and portion the rest of the dough and store the pre-shaped cookie dough balls in the freezer. Then you can pull a few out at a time when you want to make them!

  39. This article is perfect! I recently have had trouble with flat (though still chewy) cookies! I hadn’t experienced this before and I am a seasoned home baker. I had recently tried some new recipes and realized the common factor was a dough that too wet. So I tried more flour, added more egg yolk, and used bread flour and bam! Cookie are making a comeback! Thank you for talking about the effects of changing ingredients. I totally agree, everyones idea of “perfect” chocolate chip cookies are different but very tasty.

    • I’m so glad you found this article useful Katy! And glad to hear your cookies are getting figured out! I have had those times too when something I’ve made time and time again all of a sudden doesn’t work.

  40. This is a really nice informative website. I find it very interesting. Thanks for sharing.

  41. Haven’t tried YET, but I will. Years ago (I refuse to say how many) I decided to bake chocolate chip cookies. As I was getting all the ingredients out I discovered I had ZERO granulated sugar. So, I decided to go with all light brown sugar (I was REALLY wanting cookies). They turned out not quite as sweet (which was okay with us), slightly darker cookie, and chewier. We really enjoyed them and they didn’t last long.

  42. Ok so the recipe is pretty good, except it’s got way too much butter and not enough flour. I ended up adding about 1/2 a cup of flour towards the end of my batch because they kept coming out way too crispy on the outside and gooey in the middle. When I would go to SCRAPE them off the pan, they would just rip. 

    • Hi Nicole! I’d love to help you troubleshoot. This is a tested recipe that has been made with great results many times, so it sounds like you may have run into some problems. I wonder if you possibly measured out too much butter or maybe not enough flour? From the way you describe it, it sounds like an issue with your oven not being hot enough. It is common for ovens to not be calibrated properly and to say they are at a temperature but actually be too hot or too cool. I would suggest getting an oven thermometer so you can check to see what temperature your oven is actually at. I hope that helps!

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  45. Hello, I found your explanation of the science behind the Chocolate Chip cookie to be fascinating. Thanks. Years ago, and older lady we knew, made the best ever cookie she said, using the old fashioned tradition Toll House recipe. But they were very porous, light, delicate..almost a crumbly flaky almost texture. The cookie was tradition height and width but you could nearly see through it. Many loved it. Including my mom and I. We tried batch after batch, on and off for over 30 years to duplicate those treasures but couldn’t. We wondered if she mistakenly used Baking Powder instead of Baking Soda, or if she used Margarine instead of butter, Self Rising or All Purpose??? She did say that she did reduce the amount of fat (butter??) by 2 tablespoons on a half batch of the recipe. Any thoughts would be greatly appreciated. Sincerely Ms. Lewis Knoxville, TN.

    • Hi there Georgina! It sounds like its possible that she creamed the butter and sugar for a very long time. It sounds like they possibly had a lot of air beaten into them. Have you ever tried that? I would give that a try! Cream for maybe up to 6 or 8 minutes.

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  48. Which recipe would you recommend for a cookie-cake? Any do you have any helpful hints in baking one? I am teaching my grand-daughter to bake and the cookie-cake is next on her project list. I try to teach her the baking science along the way so my research brought me to your site. Very Interesting! Thanks for all the detailed info!

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  50. Hi Bettie I’m working on creating a cookie base recipe of my own and after doing some research on ratios and what not I made a batch today which I wasn’t entirely happy with. The cookie fell flat after being removed from the oven and some developed a brown sugary puddles around the cookie.

    My base consists of

    2 1/2 cups flour
    1 cup Butter
    3/4 cup brown sugar
    1/4 cup white sugar
    1 tsp baking soda
    1 tsp baking powder

    I baked them at 375 for about 10 to 12 minutes and tested both chilled dough and non chilled dough…

    Any advice/tips would be greatly appreciated

    • Hi Dana! Your ratios look pretty good! Do you by chance have an oven thermometer to make sure your oven is truly heating to 375? I feel like it might be heating much cooler than that. That would be the first thing I would investigate. You might have to set the temperature higher to get it to actually heat to 375. The higher heat will make the cookie set before it has time to spread out!

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