HEAT oven to 350°F.
SPREAD cut-side of 1 bread piece with peanut butter; reassemble loaf. Cut into 2-inch cubes; spread onto bottom of 13x9-inch baking dish sprayed with cooking spray.
BEAT pudding mixes, sugar and milk with whisk 2 min.; pour over bread. Press bread into pudding with back of spoon. Let stand 5 min. Top with chocolate.
BAKE 45 min. or until top is golden brown and center is almost set. Cool slightly. Serve topped with COOL WHIP.