LINE 9-inch square pan with foil, with ends of foil extending over sides. Mix crumbs and butter; press firmly onto bottom of prepared pan.

MICROWAVE peanut butter and chocolate in microwaveable bowl on MEDIUM 2-1/2 min. Stir until chocolate is melted and mixture is blended. Reserve 2 Tbsp. peanut butter mixture. Mix remaining peanut butter mixture with ice cream; spoon over crust. Drizzle with reserved mixture.

FREEZE 2 hours or until firm. Remove dessert from pan, using foil handles.