Instructions

• In a medium bowl, whisk together 3 cups (360 g) all-purpose flour, 1 teaspoon (4 g) baking powder, and 1/4 teaspoon kosher salt. Set aside.
• In a large bowl, beat 1 1/2 cups (300 g) granulated sugar and 1 cup (226 g) room-temperature unsalted butter with a hand mixer until light and fluffy, about 2–3 minutes.
• Add 2 large (100 g) room-temperature eggs and 1 teaspoon (4 g) pure vanilla extract to the butter mixture and beat until combined.
• Add the flour mixture to the wet ingredients and mix on low speed until a soft dough forms. Do not overmix.
• Divide the dough evenly in half.
• Add 1/4 cup (21 g) unsweetened cocoa powder to one half and mix until the chocolate dough is uniformly colored.
• On a lightly floured surface, roll the chocolate dough into a rectangle about 9 x 14 inches. Roll the plain dough to the same size.
• Place the plain dough directly on top of the chocolate dough, aligning the edges. Gently press with a rolling pin so the two layers adhere and are even. Trim the edges with a sharp knife so they are straight.
• Starting at a long side, roll the layered dough tightly into a log (jelly-roll style). Wrap the log in parchment paper or plastic wrap and freeze for 1 hour, until firm.
• About 10–15 minutes before you’re ready to bake, preheat the oven to 350°F and line a baking sheet with parchment paper.
• Unwrap the chilled log and use a sharp knife to cut it into 1/4‑inch slices. Place the slices 1 inch apart on the prepared baking sheet.
• Bake for 10–12 minutes, until the cookies are just set around the edges.
• Immediately transfer the cookies to a wire rack to cool completely.