This recipe is from Dorie Greenspan. I halved it, and baked the brownies in an 8 inch square pan. I also upped the ratio of chocolate to butter in the ganache and omitted the nutmeg.
Peanut Butter Fudge Brownies with Salted Peanuts
6 tablespoons unsalted butter, room temp
3 1/2 ounces bittersweet or semisweet chocolate, chopped
1 1/2 ounces unsweetened chocolate, chopped
3/4 cups sugar
3/4 teaspoons vanilla extract
1/8 teaspoon salt
2 large eggs
1/2 cup all purpose flour
1/2 cup roasted salted peanuts, coarsely chopped
1/2 cup chunky peanut butter (do not use natural or old-fashioned)
2 tablespoons unsalted butter, room temperature
6 tablespoons powdered sugar
1/16 teaspoon salt (tiny, tiny pinch)
1/2 tablespoon whole milk
1/2 teaspoon vanilla extract
5 ounces bittersweet or semisweet chocolate, chopped
2 tablespoons butter, unsalted
Position rack in center of oven and preheat to 325°F. Line an 8 inch baking pan with foil, leaving long overhang; butter foil. Place butter and both chocolates in a microwave safe bowl. Microwave 30 seconds; Stir and repeat until mixture is hot and smooth. Whisk in sugar, vanilla and salt, then add eggs, at a time. Fold in flour, then nuts. Spread in prepared pan and bake until tester inserted into center comes out with moist crumbs attached, about 25 minutes. Place pan on rack; cool.
Using electric mixer, beat peanut butter and the 2 tablespoons of butter in medium bowl to blend. Beat in powdered sugar and salt, then milk and vanilla. Spread frosting over brownies. Chill for about an hour to set frosting (this makes spreading the chocolate easier).
Place chocolate and the 2 tablespoons of reserved butter in a small microwave-safe bowl. Heat on high 30 seconds. Stir and repeat 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 15 brownies