Mix melted butter and chocolate graham cracker crumbs. Press into an 8 or 9 inch pie plate. Place in freezer.
Using a double boiler, melt marshmallows and 2/3 cup heavy cream, stirring frequently. Once melted, remove from heat and add peppermint extract and green food coloring if desired. Set aside and allow to cool slightly.
With an electric mixer, beat 1 cup heavy cream until stiff peaks form. Gently fold whipped cream into marshmallow mixture. Fold in 3/4 of the crushed Oreos and reserve 1/4 of them for topping.
Pour mixture onto crust. Sprinkle top with remaining crushed Oreos. Place back in freezer for at least two hours before serving.
You can buy graham crumbs directly from the store or you can crush whole graham crackers by placing them in a food processor. If you do not have a food processor, you can also place graham crackers in a large ziptop bag and crush them with a rolling pin.