Sprinkle crushed cookies in bottom of an 8-inch square baking dish.
Combine milk, pudding mix, and crème de menthe in a blender. Process until smooth. Pour into a bowl. Let stand 1 to 2 minutes or until pudding mixture thickens. Fold in half of container of whipped topping and peppermint patties. Spoon into prepared dish. Cover and chill 2 hours.
Shave chocolate with a vegetable peeler to get 2 tablespoons chocolate curls. Spread remaining whipped topping over mousse, and sprinkle with chocolate curls.