LINE 13x9-inch pan with foil, with ends of foil extending over sides. Crush 20 cookies; sprinkle onto bottom of prepared pan.
SPREAD ice cream over crumbs in pan; top with Cool Whip and grated chocolate.
FREEZE 3 hours. Remove from freezer 15 min. before serving. Let stand at room temperature to soften slightly. Use foil handles to lift dessert from pan before cutting into squares. Cut remaining cookies in half; use to garnish dessert squares.