- 2 sticks (1 cup) unsalted butter
- 8 ounces fine-quality bittersweet chocolate (not unsweetened), coarsely chopped
- 1 1/4 cups all-purpose flour
- 1 teaspoon baking powder
- 1/2 teaspoon salt
- 2 cups sugar
- 4 large eggs
- 2 teaspoons vanilla
Melt butter and chocolate in a medium heatproof bowl set over a saucepan of simmering water, stirring occasionally, until smooth.
Whisk together flour, baking powder, and salt in a small bowl.
Whisk together sugar, eggs, and vanilla in a large bowl, then pour in chocolate mixture, whisking until combined well. Whisk in flour mixture, set aside.
Chocolate Chip Cookie Dough
1 1/2 cups all-purpose flour
3/4 teaspoon baking soda
3/4 teaspoon salt
1 1/2 sticks (3/4 cup) unsalted butter, melted and cooled slightly
3/4 cup packed light brown sugar
1/2 cup granulated sugar
2 large eggs
3/4 teaspoon vanilla
1 1/4 cups semisweet chocolate chips (8 ounces)
Put oven rack in middle position and preheat oven to 350°F. Grease a 13- by 9- by 2-inch baking pan and line bottom and sides with wax paper, then butter paper.
Spread brownie batter evenly in pan. Bake for 35 minutes while mixing cookie dough, remove from oven and let cool slightly.
Make chocolate chip dough:
Whisk together flour, baking soda, and salt in a small bowl.
Beat together butter and sugars in a large bowl with an electric mixer at high speed until pale and fluffy, 2 to 3 minutes. Lightly beat 1 egg with a fork in a small bowl and add 1 3/4 tablespoons of it plus remaining whole egg to butter mixture, beating with mixer until creamy. Beat in vanilla. Reduce speed to low and mix in flour mixture until just blended, then stir in chips.
Top brownies evenly with spoonfuls of cookie dough, spreading gently with back of spoon to form an even layer. If the brownies are not cooked the dough will sink into the batter, it also helps when spreading the cookie dough.
Bake until a wooden pick or skewer inserted in center comes out with moist crumbs adhering, about 35-45 minutes longer. Cool completely in pan on a rack, about 2 hours. Invert onto a cutting board, remove paper, and cut into bars.