Ingredients

3 1/4 c. (390 g.) all-purpose flour

1 tsp. baking powder

1/2 tsp. kosher salt

1 c. (2 sticks) unsalted butter, softened

1 c. (200 g.) granulated sugar

1 large egg

1 large egg yolk

1 tsp. pure vanilla extract

1/4 c. (20 g.) unsweetened cocoa powder

Preparation

Step 1In a large bowl, whisk flour, baking powder, and salt. In the large bowl of a stand mixer fitted with the paddle attachment (or in another large bowl using an electric mixer), beat butter and granulated sugar on medium-high speed until creamy. Add egg and egg yolk and beat until incorporated. Scrape down sides and beat in vanilla. Add dry ingredients and beat again until just combined. Step 2Transfer one-half of dough to a work surface. To remaining dough in bowl, add cocoa powder and beat until just combined. Step 3Shape each half of dough into rectangles that are 2" tall and wide and about 5" long, making both as close to the same size and shape as possible. Wrap each half in plastic wrap and refrigerate until chilled, at least 1 hour or up to 2 days. Step 4Cut each log into thirds lengthwise. Cut each piece into thirds lengthwise again (you should have 9 long strips from each block). Tim any rounded edges to help make perfect squares. Step 5Place a strip of vanilla dough, then a chocolate strip, then another strip of vanilla right next to each other. Stack a piece of chocolate, then vanilla, then another chocolate on top. Stack a third row of vanilla, chocolate, and another vanilla. Repeat to make a second block of dough, starting with chocolate. Wrap doughs in plastic wrap and refrigerate until chilled, at least 1 hour or up to 2 days. Step 6Preheat oven to 350°. Line 2 baking sheets with parchment. Cut dough into 1/3"-thick squares and arrange on prepared sheets. Step 7Bake cookies until edges just start to turn golden and centers feel set, 10 to 12 minutes. Let cool on wire racks.Step 8Make Ahead: Cookies can be made 5 days ahead. Store in an airtight container at room temperature.

Have you made these yet? Let us know how it went in the comments below!