HEAT oven to 350ºF.
PREPARE brownie batter as directed on package; pour into 13x9-inch baking dish sprayed with cooking spray. Bake 40 min. or until toothpick inserted in center comes out with fudgy crumbs. (Do not overbake.) Cool completely.
MAKE 24 holes in top of brownie, leaving thin layer of brownie on bottom on each. Reserve removed pieces.
BEAT pudding mixes and milk in medium bowl with whisk 2 min. Add 2/3 cup peanut butter; mix well. Stir in COOL WHIP. Spoon onto brownie; top with reserved brownie pieces.
MICROWAVE remaining peanut butter in microwaveable bowl on HIGH 30 sec.; stir. Drizzle over dessert. Refrigerate 2 hours or until chilled.