Makes about 40 2 1/2-inch cookies.
For the cookies
1 cup (4 1/2 oz./128 g) unbleached all-purpose flour
1 1/4 cups (5 oz./142 g) cake flour, sifted
2/3 cup (2 oz.) unsweetened natural cocoa powder, sifted
3/4 tsp. table salt
1/4 tsp. baking powder
16 Tbs. (8 oz./227 g) unsalted butter, softened
1 1/4 cups (8 3/4 oz./248 g) granulated sugar
1 large egg, at room temperature
1 yolk from large egg, at room temperature
1 tsp. pure vanilla extract
Make the cookie dough
- Have ready several sheets of parchment and a cookie sheet. Whisk the all-purpose and cake flours, cocoa powder, salt, and baking powder in a medium bowl until well blended.
- Put the butter in the bowl of a stand mixer fitted with the paddle attachment (or in a large bowl using an electric handheld mixer fitted with wire beaters) and beat on medium speed until smooth, about 1 minute. Add the sugar and continue beating until fluffy and lighter in color, about 2 minutes. Add the egg, yolk and vanilla and beat until blended, about 1 minute. Add the flour mixture and beat on low speed until the dough forms moist clumps.
- Scrape the dough onto the work surface and portion into two approximately equal piles. Put one pile of the dough in the center of a sheet of parchment. Cover with another piece of parchment and press down on the dough to flatten. Using a rolling pin, roll the dough between the parchment to a 1/4-inch (6 mm) thickness, turning, lifting, and repositioning the parchment and lightly flouring throughout the rolling. Slide the dough and parchment onto a cookie sheet and refrigerate. Repeat with more parchment and the remaining dough, stack on top of the other one, and refrigerate until firm, at least 1 hour.