In a saucepan mix the gelatin and water let sit 1 minute. Cook over low heat until dissolved, stirring constantly. In a mixing bowl, combine the gelatin mixture, marshmallow, and creme de menthe and mix well. Refrigerate until mixture mounds when dropped from spoon. In a separate mixing bowl, whip cream until soft peaks form. Fold whipped cream into gelatin mix. Add candies and mound into pie crust. Garnish with whipped cream and additional candies, optional. Refrigerate overnight.