STIR boiling water into gelatin in large bowl at least 2 min. until completely dissolved. Add enough ice cubes to cold water to measure 1-1/2 cups. Add to gelatin; stir until ice is completely melted. Remove 2 cups of the gelatin; place in small bowl. Refrigerate 5 min. or until gelatin is the consistency of unbeaten egg whites. Carefully spoon into crust. Refrigerate 10 min.
MEANWHILE, add 2 cups of the whipped topping to remaining gelatin; stir with wire whisk until well blended. Refrigerate 10 min. or until mixture is thick and will mound. Carefully spoon over gelatin layer in crust.
REFRIGERATE at least 3 hours or until firm. Serve topped with the remaining whipped topping. Store leftover dessert in refrigerator.