Heat oven to 350ºF. Line two 8-inch or 7-inch round pans with circles of parchment and spray with cooking spray. (7-inch pans will create thicker layers). Divide brownie batter between the two pans. Bake until just cooked through, about 35 min. Cool brownies completely.
In a mixing bowl beat together the peanut butter, butter, cream cheese and salt. Mix in the confectioners’ sugar, mixture will be stiff, then add the milk and beat until smooth.
If piping, transfer frosting to a piping bag fitted with a #825 open star tip. Remove parchment from the bottoms of the brownie cakes and place one on a serving platter. Pipe or spread half the frosting on the surface. Place the other brownie cake on top and pipe or spread the remaining frosting on top. Sprinkle with chopped peanuts.
A boxed brownie mix just took on a whole new meaning!The nutrition is calculated for 8 servings.