LINE 8x4-inch loaf pan with foil, with ends of foil extending over sides. Spread ice cream onto bottom of pan. Mix cookie crumbs and margarine; sprinkle over ice cream. Cover with ends of foil; gently press crumb mixture into ice cream.
FREEZE 6 hours or until firm.
INVERT dessert onto plate when ready to serve; remove pan and foil. Frost dessert with Cool Whip. Coarsely grate chocolate square; sprinkle over dessert.
serving size = 1 piece (85 g)