1. Heat oven to 350 degrees F. Mix flour, baking powder and salt in small bowl.
2. Melt half of semisweet chocolate, the unsweetened chocolate and butter in top of double boiler; stir until smooth.
3. Beat sugar, eggs and espresso on high speed in bowl until ribbonny, 3 minutes. Fold in melted chocolate. Stir in flour mixture. Fold in remaining chocolate pieces.
4. Drop batter, 1 tablespoon per cookie, 2 inches apart, on greased baking sheets.
5. Bake in 350 degrees F oven 12 minutes, until puffed and crackly. Cool slightly on sheets. Transfer to racks to cool.