In a small bowl, mix crushed cookies and melted butter. Reserve 3 tablespoons for topping. Press remaining mixture onto bottom of a greased 8-in. square baking dish. Refrigerate 30 minutes.
In a large microwave-safe bowl, sprinkle gelatin over 1/2 cup cold milk; let stand 1 minute. Microwave on high for 30-40 seconds. Stir until gelatin is completely dissolved. Add marshmallows; cook 1-2 minutes longer or until marshmallows are puffed; stir until smooth. Stir in creme de menthe. Refrigerate 15-20 minutes or until cold but not set, stirring often.
Meanwhile, in a small bowl, gradually beat cream cheese until smooth. In another bowl, whisk pudding mix and remaining cold milk (1 1/4 cups). Gradually beat into cream cheese.
In a large bowl, beat heavy cream until soft peaks form; fold into marshmallow mixture. Spoon half of the mixture over prepared crust; refrigerate 10 minutes. Layer with pudding mixture and remaining marshmallow mixture; top with reserved crumbs. Refrigerate 2 hours or until set.
Notes
Chill layers in the freezer to shorten preparation time
Use a food processor to get the Oreos crushed into a fine crust (I did not this time and ended up with a crumbly crust because the pieces were too large)