1. Combine 1-1/2 cups cookie crumbs and butter; press onto bottom of 9-inch square pan. Refrigerate 15 min.
2. Meanwhile, beat peanut butter, dry vanilla pudding mix and 1-1/2 cups milk in medium bowl with mixer until blended.
3. Beat chocolate pudding mix and remaining milk in separate medium bowl with mixer 2 min. Blend in melted chocolate; spread over crust.
4. Reserve 1 Tbsp. of the remaining cookie crumbs for topping; sprinkle remaining crumbs over chocolate layer. Cover with marshmallows, then spread with peanut butter mixture.
5. Refrigerate 3 hours. Top with COOL WHIP just before serving; sprinkle with reserved cookie crumbs.