Combine marshmallows and milk in top of double boiler; bring water to a boil. Reduce heat to low; cook until marshmallows melt, stirring frequently. Remove from heat; coo, stirring occasionally. Add creme de menthe and creme de cacao; fold in whipped cream. Spread ice cream evenly in piecrust, and pour marshmallow mixture over ice cream. Freeze at least 6 hours. Garnish with additional whipped ----