Preparation

• Step 1.
• Melt unsweetened chocolate, butter, and 1 cup chocolate chips in a heavy saucepan over low heat, stirring occasionally. Cool.
• Step 2.
• Stir together flour, cocoa, baking powder, and salt.
• Step 3.
• Beat together sugar, eggs, and vanilla with an electric mixer until pale and frothy, about 2 minutes. Mix in melted chocolate and then flour mixture at low speed until combined well. Stir in remaining cup chips. Chill, covered, until firm, about 2 hours.
• Step 4.
• Preheat oven to 350°.
• Step 5.
• Roll heaping teaspoons of dough into 1-inch balls with dampened hands and arrange 2 inches apart on ungreased baking sheets. Bake in batches in middle of oven until puffed and set, about 10 minutes (cookies will be soft in center). Transfer to racks to cool.