For crust, stir melted butter and crushed cookie together in a small bowl. Reserve ½ cup dry cookie crumbs for garnish. Press mixture into the bottom of a 9x13 pan.
Once ice cream is softened, spread over crust, and freeze for 2 hours
Drizzle warm chocolate fudge sauce over ice cream, then freeze for 1 hour.
Spread on whipped topping over ice cream, and sprinkle Oreo crumbs on top. Freeze again for at least 2 hours. Before serving, let sit out for 15 minutes.
Notes
A regular size package of Oreo cookies is about 33 cookies. However, if you add more or less the recipe will still work. It just depends on how thick you want your Oreo crust to be and if your pan is big enough.