1 pkg. Oreos, crushed
1/4 c. butter, melted
1/4 c. green creme de menthe
1 (8 oz.) jar marshmallow creme
2 c. heavy cream, whipped or Cool Whip

Combine first two ingredients - press 1/2 of mixture into 9 x 13 inch pan. Add creme de menthe to marshmallow creme until well blended - fold into whipped cream. Pour onto chocolate crust. Sprinkle remaining crumbs over top. Freeze until ready to serve.