Ingredients for 2 dozen
1/8 teaspoon salt
¼ cup unsweetened cocoa
¾ cup packed brown sugar
1 teaspoon instant espresso granules
1 ¼ cups powdered sugar, divided
1 ¼ teaspoons baking powder
1 ½ ounces unsweetened chocolate, chopped
1 ½ teaspoons vanilla extract
2 large egg whites
3 tablespoons light-colored corn syrup
4.5 ounces all-purpose flour (about 1 cup)
5 ¼ teaspoons canola oil
Weigh or lightly spoon flour into dry measuring cups; level with a knife. Combine flour, ¾ cup powdered sugar, cocoa, baking powder, and salt in a medium bowl; stir with a whisk. Combine oil and chocolate in a small saucepan over low heat; cook until chocolate melts, stirring constantly. Add espresso granules to pan; stir until blended. Remove from heat. Pour chocolate mixture into a large bowl; cool 5 minutes. Stir in brown sugar, syrup, and vanilla. Add egg whites, stirring with a whisk. Add flour mixture to egg mixture, stirring gently just until combined. Cover; chill at least 2 hours or overnight.
Preheat oven to 350°.
Roll dough into 1-inch balls. Dredge balls in remaining ½ cup powdered sugar; place balls 2 inches apart on 2 baking sheets lined with parchment paper. Bake at 350° for 10 minutes or until tops are cracked and almost set. Cool cookies on pan 2 minutes or until set; remove from pan. Cool cookies on a wire rack.