Crust: Preheat oven to 350° F. Lightly spray a 10-inch springform pan with nonstick vegetable coating.
In a medium bowl, mix cookie crumbs with melted butter. Pack over bottom of prepared pan. Bake in preheated oven 6 minutes. Set aside to cool.
Filling: In medium saucepan, bring liqueur, cream, and butter to a boil. Remove heat and mix in cookie crumbs. Fold in melted chocolate. When thoroughly incorporated, fold in whipped topping. Pour into cooled pie crust, filling pan to the top and spreading evenly. Freeze for 90 minutes.
Icing: Whip cream until very stiff; fold in liqueur and syrup. Remove rim from springform pan. Spread icing evenly over top and sides. Refrigerate at least 20 minutes before serving.Makes 6 to 8 Source: