- 3/4 cup (1 1/2 sticks) unsalted butter
- 7 ounces bittersweet or semisweet chocolate, chopped
- 3 ounces unsweetened chocolate, chopped
- 1 1/2 cups sugar
- 1 1/2 teaspoons vanilla extract
- 1/4 teaspoon salt
- 4 large eggs
- 1 cup all purpose flour
- 1 cup roasted salted peanuts, coarsely chopped
- 1 cup chunky peanut butter (do not use natural or old-fashioned)
- 1/2 cup (1 stick) unsalted butter, divided, room temperature
- 3/4 cup powdered sugar
- 1/8 teaspoon salt
- 1/8 teaspoon ground nutmeg
- 1 tablespoon whole milk
- 1 teaspoon vanilla extract
- 7 ounces bittersweet or semisweet chocolate, chopped
- Position rack in center of oven and preheat to 325°F. Line 13x9x2-inch metal baking pan with foil, leaving long overhang; butter foil.
- Place 3/4 cup butter in heavy large saucepan. Add both chocolates; stir over low heat until smooth. Remove from heat. Whisk in sugar, vanilla, and salt, then eggs, 1 at a time. Fold in flour, then nuts. Spread in prepared pan. Bake until tester inserted into center comes out with moist crumbs attached, about 30 minutes. Place pan on rack; cool.
- Using electric mixer, beat peanut butter and 1/4 cup butter in medium bowl to blend. Beat in powdered sugar, salt, and nutmeg, then milk and vanilla. Spread frosting over brownies.
- Stir chocolate and 1/4 cup butter in heavy small saucepan over low heat until smooth. Drop ganache all over frosting; spread to cover. Chill until set, about 1 1/2 hours. Do ahead Can be made 1 day ahead. Cover and keep chilled.
- Using foil as aid, transfer brownie cake to work surface; cut into squares. Bring to room temperature; serve.