Instructions

Prep:

1. At least 30 minutes before mixing your dough, set out the butter to come to room temperature. Measure out the rest of the ingredients. 
2. Prepare an 8-inch (20 cm)* square baking pan with parchment or non-stick spray. 
3. Position an oven rack in the center position. Preheat the oven to 350°F/175°C.

To Make the crumb bars:

1. In the bowl of a stand mixer fitted with a paddle attachment, or in a large bowl with a hand mixer, cream together the soft butter (113 grams/ ½ cup) and sugar (50 grams/ ¼ cup) on medium speed until light and fluffy- about 2 minutes. Scrape down the sides and bottom of the bowl halfway through. 
2. In a separate mixing bowl, whisk together the salt (¼ teaspoon) and flour (128 grams/ 1 cup + 1 tablespoon).
3. Add the flour mixture to the mixing bowl and mix on medium/low speed until just incorporated. The dough will likely be a bit crumbly looking, but should still look moist and hold together if pressed together in your hand. If it does not hold together, you can add about 1-2 tablespoons of milk or water until it holds together when pressed. 
4. Divide out about 75 grams (½ cup) of the dough and set aside. Press the remaining dough evenly into the bottom of the pan.
5. Spread your jam of choice (140 grams/ ½ cup) over the top of the dough. 
6. Crumble the remaining shortbread dough over the top of the jam. If using, sprinkle chopped nuts (25 grams/ ¼ cup) evenly over the top. No need to toast the nuts first as they will toast in the oven. 
7. Bake for 26-30 minutes, until the center is set and the shortbread is golden brown.
8. Set the pan on a cooling rack for at least 15 minutes. 
9. If desired, drizzle with a powdered sugar glaze before slicing. 
10. Cut into 9 bars. Store leftover bars wrapped in foil or plastic wrap at room temperature for up to 4 days.