Stir 1-1/2 cups flour, 6 tablespoons cocoa, 2 teaspoons baking powder and 1/2 teaspoon salt in a medium-size bowl. Beat 1/2 cup butter and 1-1/3 cup sugar in second bowl until light and fluffy. Beat in 2 eggs one at a time. Beat in peanut butter until well blended. On low speed, beat half flour mixture, then half milk, into butter mixture. Repeat. Place mixture in large plastic bag; snip off end. Pipe over cheesecake layer to cover, gently spreading to smooth top. Place foil tent over top, crimping edges. Do not let foil touch top of batter.