About 2 1/4 cups flour
11 tablespoons unsweetened cocoa powder, sifted (not Dutch-process)
3 tablespoons plus 1 tablespoon (5.6 grams) instant espresso powder, such as Medaglia d’Oro brand
2 teaspoons baking powder
11 1/2 tablespoons (scant 1 1/2 sticks) unsalted butter, at room temperature
About 1 cup plus 1/2 cup sugar
1 tablespoon vanilla extract
2 large eggs
14 ounces milk chocolate, coarsely chopped
For the cookies: Preheat the oven to 350 degrees. Line 2 baking sheets with parchment paper.
Combine the flour, cocoa powder, 3 tablespoons of the instant espresso powder and the baking powder in a medium bowl; whisk to mix well.
Combine the butter and 1 cup of the sugar in the bowl of a stand mixer or hand-held electric mixer. Beat on medium speed for 5 minutes, until light and fluffy. Add the vanilla extract, then the eggs one at a time, beating well after each addition. Reduce the speed to low, then add the flour mixture; beat until almost all streaks of flour are gone. Stop the mixer to add the milk chocolate chunks; beat on low speed until just combined.
For sprinkling: Combine the remaining 1/2 cup sugar with the remaining tablespoon of instant espresso powder in a shallow bowl; mix well.
Scoop the dough into mounds (about 1 tablespoon), then dip or roll them in the sugar-espresso mixture. Place them 2 inches apart on the lined baking sheets. Bake one sheet at time for 10 minutes, until the cookies are softly set, then cool completely (still on the sheet) on a wire rack. Repeat as needed to use all the dough.