Mix crushed cookies with butter and press into a 23 cm pie pan. Chill. Stir chocolate ice cream to soften and blend in quarter cup coffee liqueur. Spoon into pie shell. Sprinkle with crushed Heath Bars and place in freezer 1 hour. Soften vanilla ice cream and add quarter cup coffee liqueur. Spoon over the chocolate mixture. Freeze overnight. Garnish by piping whipped cream around the pie. Cut into wedges and serve with a drizzle of coffee liqueur over the top.