| 1/2 cup peanut butter 1/2 cup butter 1 cup packed brown sugar 1/2 cup white sugar 2 eggs 3/4 teaspoon vanilla extract 2 1/2 cups sifted all-purpose flour | 3 teaspoons baking powder 1/2 teaspoon salt 1 cup milk 1/8 cup butter 3 cups confectioners sugar 4 1/2 tablespoons evaporated milk 1 1/2 teaspoons vanilla extract |