1. Crush 18 cookies; mix with butter. Press onto bottom and up side of 9-inch pie plate.
2. Spread ice cream onto bottom of crust. Freeze 3 hours.
3. Remove pie from freezer 15 min. before serving. Top with whipped topping and grated chocolate. Place 1 of the remaining cookies in center of pie. Cut remaining cookies in half; use to garnish pie.