- 1 stick (1/2 cup) unsalted butter
- 8 ounces fine-quality milk chocolate, chopped
- 3/4 cup packed light brown sugar
- 1 teaspoon pure vanilla extract
- 2 large eggs
- 3/4 cup all-purpose flour
- 1 tablespoon unsweetened cocoa powder
- 1/2 teaspoon salt
- 1/4 teaspoon baking powder
- Put oven rack in middle position and preheat oven to 350°F. Butter and flour a 9-inch square baking pan.
- Melt butter and half of chocolate in a 1 1/2-quart heavy saucepan over low heat, stirring, until smooth. Remove from heat and cool to lukewarm. Stir in brown sugar and vanilla. Add eggs 1 at a time, beating well after each addition, until mixture is glossy and smooth.
- Whisk together remaining ingredients, then stir into chocolate mixture. Stir in remaining chocolate.
- Spread batter in pan and bake until a wooden pick or skewer comes out with a few moist crumbs adhering, 25 to 30 minutes.