Crush the Oreo cookies in your food processor or in a plastic bag with a rolling pin until they resemble fine crumbs. Add them to a bowl with the melted butter and mix to combine.
Pour the mixture into a 9-inch pie pan and press into the bottom and up the sides to form a crust.
Set the crust aside in the refrigerator while you make the filling.
In a large bowl, whip the cream cheese with a hand mixer until nice and creamy.
Add the sweetened condensed milk in a steady stream while the mixer is running, mixing well until it's completely integrated (scrape down the sides of the bowl).
Whip in the Creme de Menthe and food colouring, scraping down the sides of the bowl to make sure everything is evenly incorporated.
Gently fold in the whipped cream (be sure to whip it to stiff peaks first!) with a rubber spatula. You can also use whipped topping, if desired.
Dollop the mixture into the pie pan over the Oreo crust and smooth it out as best you can. Top with a few more crushed Oreo cookies.
Place in the freezer for 4 hours or overnight.
If you let it freeze overnight, remove it from the freezer for 20 minutes before slicing and serving.
Slice with a hot knife for nice clean slices.