Preheat oven to 350 F. In a medium bowl, whisk together flour, cocoa powder, espresso powder, baking powder, and salt. Set aside a half cup of the chocolate chips. Place remaining chocolate chips in a heatproof bowl and microwave 20 to 30 seconds at a time, stirring in between until almost melted, then stirring one last time. Set melted chocolate aside to cool. In a large bowl with an electric mixer, beat butter and sugar until light and fluffy. Continue beating while adding eggs, vanilla, and melted chocolate. With mixer on low, gradually add flour mixture, until just combined. Drop spoonfuls of dough 3 inches apart onto ungreased baking sheets. Top each cookie with some of the remaining chocolate chips. Bake approximately 13 to 15 minutes, rotating sheets halfway through, until edges are dry and tops are cracked. Let stand 3 minutes, then transfer to wire racks to cool. Makes about 2 dozen cookies.
Finely ground espresso or dark-roast coffee can be substituted for the espresso powder.
Per serving: 314 calories, 16 grams fat (7 grams saturated fat), 51 milligrams cholesterol, 242 milligrams sodium, 42 grams total carbohydrates, 1.5 grams fiber, 3 grams protein.
