LINE 9-inch square pan with foil extending over edges to form handles. Microwave 4 oz. chocolate and 5 Tbsp. of the butter in large microwavable bowl on HIGH 2 minutes or until butter is melted. Stir until chocolate is completely melted. Add crumbs; mix well. Press firmly onto bottom of prepared pan. Refrigerate 10 minutes.
MICROWAVE 1/3 cup water and remaining 5 Tbsp. butter in large microwavable bowl on HIGH 1 minute or until butter is melted. Add dry pudding mix; stir 2 minutes or until completely dissolved. Gradually add powdered sugar, stirring until well blended after each addition. Spread over crust. Refrigerate 15 minutes or until firm.
MICROWAVE remaining 4 oz. chocolate and cream in medium microwavable bowl on HIGH 2 minutes. Stir until chocolate is completely melted and mixture is well blended. Spread over pudding layer. Refrigerate 2 hours or until set. Lift out of pan onto cutting board. Cut into 24 bars to serve. Store leftover bars in refrigerator.