- Combine chocolate and butter in top of a double boiler set over hot but not boiling water.
- Stir until both are melted and smooth.
- Remove from heat, and set aside.
- Beat eggs, sugar and vanilla in a large mixing bowl using an electric mixer on high speed until light and thick, for about 5 minutes.
- In a separate bowl, combine flour, baking powder and salt.
- Mix well.
- Reduce mixer speed to low, and slowly add chocolate to eggs.
- Fold in flour mixture—dough will be thin.
- Transfer to a bowl, cover and refrigerate for at least 4 hours, or overnight.
- Preheat oven to 350°F.
- Lightly spray cookie sheets with nonstick cooking spray.
- Scoop heaping tablespoons of dough onto cookie sheets, placing them about 3 inches apart.
- Bake for about 15 minutes, or until center of cookie is firm to touch.
- Remove from oven, set aside to cool on wire racks and serve as close to baking time as possible.