Finely crush cookies; set aside. Microwave butter in large microwavable bowl on HIGH 30 seconds or until butter is melted. Add crushed cookies; mix well. Press crumb mixture firmly onto bottom of 9-inch square pan.
Mix dry pudding mix, sugar and boiling water until well blended. Pour over crust; spread to completely cover crust. Sprinkle with peanuts and marshmallows.
Place chocolate squares in microwavable bowl. Microwave on HIGH 45 seconds; stir until chocolate is completely melted. Drizzle over pudding mixture. Refrigerate 1 hour or until set. Cut into 20 bars to serve. Store leftover bars in refrigerator.