In a bowl crush 20 cream-filled chocolate cookies to make 1 3/4 cups of crumbs. Reserve 1/4 cup for garnish. Paat the remaining crumbs on the bottom and sides of a buttered 9-inch pie tin. Set the crust aside. In a medium bowl combine the condensed milk, creme de menthe, creme de cacao, and heavy cream. Mix thoroughly. Pour the mixture into the crust. Top with the remaining crumbs. Freezze the pie for 6 hours. The pie will not freezze solid. Garnish with mint, if desired.