Prepare the Crust: Place Oreo cookies into a food processor and pulse until they become fine crumbs. If you don't have a processor, place cookies in a sealed bag and crush them using a rolling pin. Transfer crumbs to a mixing bowl. Drizzle melted butter over the crumbs and stir until well coated and sand-like in texture. Press this mixture firmly into the bottom of a 9×13 pan, creating a smooth, even crust. Place the dish into the freezer for 10-15 minutes to firm it up.

Add the Ice Cream Layer: Remove the ice cream from the freezer for 10-15 minutes so it softens slightly and becomes spreadable. Spoon the softened ice cream over the cold crust. Use a spatula to spread the ice cream into a thick, even layer. Return the pan to the freezer for at least 1 hour so the ice cream layer fully hardens.

Prepare and Add the Chocolate Fudge Layer: Warm the fudge topping just enough to make it pourable — usually 10-20 seconds in the microwave. It should be thick but spreadable, not hot. Optionally stir in a small amount of heavy cream to help with smooth spreading. Pour or spoon the fudge topping over the frozen ice cream layer. Use spatula strokes to lightly smooth it across the surface. Freeze again for 45-60 minutes, or until the chocolate layer is set.

Add the Whipped Topping Layer: Spread the whipped topping in a fluffy, even layer over the fudge. Press lightly to fill any air gaps, but do not squash the airy texture. Smooth the top. Return pan to freezer for at least 2 hours for the entire cake to properly firm.

Garnish and Freeze Until Serving: Right before serving, add crushed Oreos on top — this keeps them crisp. Drizzle chocolate or add sprinkles if desired. Cover loosely with plastic wrap and keep frozen until ready to slice.