Line 13x9-inch pan with foil, with ends of foil extending over sides; spray with cooking spray. Microwave 5 oz. chocolate and 1/2 cup butter in medium microwaveable bowl on HIGH 2 min. or until butter is melted; stir until chocolate is completely melted and mixture is well blended. Stir in graham crumbs, nuts and 1 cup coconut; press onto bottom of prepared pan. Refrigerate 15 min.