For the Brownies:
Position rack in center of oven and preheat oven to 325°F/160°C. Line a 9 x 13 x 2-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 confectioners' sugar, salt, and nutmeg, then milk and vanilla. Spread frosting over brownies.
Stir the 7 oz. chocolate and the 1/4 cup butter in a heavy small saucepan over low heat until smooth. Drop ganache all over frosting; spread to cover. Chill until set, about 1 1/2 hours.
Using foil as aid, transfer brownie cake to work surface; cut into squares. Bring to room temperature; serve.
Makes 30 brownies.
Ganache can be made 1 day ahead. Cover and keep chilled.
Source: Bon Appétit January 2007-Recipe by Dorie Greenspan
Date: January 30, 2007