Martha Stewart Recipe
Preheat oven to 350 degrees. Heat chopped chocolate and butter in a microwave-safe bowl in 20-second increments, stirring in between, until almost melted; do not overheat. In another bowl, whisk together flour, baking powder, and salt.
In a mixing bowl, beat eggs, brown sugar, and vanilla on high speed until light and fluffy. Reduce speed to low; beat in melted chocolate. Mix in flour mixture until just combined. Stir in chocolate chunks.