Instructions

• Prepare the brownies according to the directions on the box and bake them in an 8-, 9- or 10-inch springform pan. Allow the brownies to cool completely in the pan; do not remove the sides.
• Make the peanut-butter crunch layer: in a heavy saucepan over low heat, melt 1/4 cup butter and 1 cup chocolate chips, stirring until smooth (or melt slowly in the microwave, stirring frequently). Remove from heat and stir in 1 cup peanut butter until combined. Fold in 1 1/2 cups crushed corn flakes until evenly coated. Spread this mixture evenly over the cooled brownie layer and set aside.
• Make the mousse layer: in a heavy saucepan over low heat, melt 4 oz semi-sweet chocolate with 1/4 cup milk and 1 cup marshmallows (chocolate or regular), stirring until smooth and the marshmallows are fully melted. Remove from heat and let the chocolate mixture cool completely, about 30 minutes, stirring occasionally.
• While the chocolate mixture cools, chill a mixing bowl (optional) and beat 1 cup whipping cream on high speed until stiff peaks form.
• Gently fold the cooled chocolate–marshmallow mixture into the whipped cream until uniform, keeping as much air as possible in the whipped cream. Spread the mousse evenly over the peanut-butter crunch layer.
• Refrigerate the pie for at least 3 hours to set.
• To serve, run a thin knife around the edge of the springform, release and remove the pan sides, slice, and serve.