4 ounces Unsweetened chocolate; chopped
3 cups Semisweet chocolate chips
1/2 cup unsalted butter; cut into bits
1/2 cup All-purpose flour
1/2 teaspoon Double-acting baking powder
1/4 teaspoon Salt
4 large Eggs; at room temperature
1 1/2 cups Sugar
1 tablespoon Instant espresso powder
2 teaspoons Vanilla
In a metal bowl set over a saucepan of simmering water melt the unsweetened chocolate, 1 1/2 cups of the chocolate chips, and the butter, stirring until the mixture is smooth, and remove the bowl from the heat. In a small bowl stir together the flour, the baking powder, and the salt. In a bowl beat the eggs with the sugar until the mixture is thick and pale and beat in the espresso powder and the vanilla. Fold the chocolate mixture into the egg mixture, fold in the flour mixture, and stir in the remaining 1 1/2 cups chocolate chips. Let the batter stand for 15 minutes.
Drop the batter by heaping tablespoons onto baking sheets lined with parchment paper and bake the cookies in the middle of a preheated 350 degree oven for 8 to 10 minutes, or until they are puffed and shiny and cracked on top. Let the cookies cool on the baking sheets, transfer them to racks, and let them cool completely.
Source: Sara Moulton