Lightly grease a 9×13-inch glass or ceramic baking dish with nonstick spray or a thin smear of butter, especially on the sides, to help the crust release but not stick too firmly.

Place the Oreo cookies in a food processor and pulse until you have fine crumbs. Alternatively, place the cookies in a sturdy zip-top bag and crush them with a rolling pin until finely ground.

Transfer the Oreo crumbs to a mixing bowl. Pour in the melted butter and stir until all the crumbs are evenly moistened and look like damp sand.

Pour the Oreo mixture into the prepared dish. Use the bottom of a measuring cup or your fingers to press the crumbs into an even layer, all the way to the edges, packing it firmly but not rock hard. Refrigerate for 15–20 minutes to help the crust firm up while you prepare the cream cheese layer.

In a medium bowl, beat the softened cream cheese with an electric mixer until smooth and fluffy. Add the granulated sugar, milk, and vanilla extract, and beat again until fully combined and no lumps remain.

Gently fold 1 1/2 cups of whipped topping into the cream cheese mixture with a spatula until light and smooth, taking care not to deflate it.

Remove the chilled crust from the refrigerator. Spoon the cream cheese mixture over the Oreo crust in several dollops, then gently spread it into an even layer all the way to the edges, trying not to disturb the crust. Return the pan to the fridge while you prepare the pudding.

In a large mixing bowl, whisk together the instant chocolate pudding mixes and cold milk for about 2 minutes, until the mixture begins to thicken but is still pourable. Let it sit for 3–5 minutes to thicken slightly more before layering.

Take the pan from the refrigerator and carefully pour or spoon the thickened pudding over the cream cheese layer. Work in sections and gently spread the pudding to the edges to form an even layer.

Let the pudding sit for 5–10 minutes to set a bit more. Then spread 1 1/2 to 2 cups of whipped topping evenly over the pudding to create a smooth, fluffy top layer.

Sprinkle chocolate chips, mini chocolate chips, or shaved chocolate evenly over the whipped topping. Add crushed Oreos, chocolate curls, or a light dusting of cocoa powder if desired for extra flavor and decoration.

Cover the dish tightly with plastic wrap and refrigerate for at least 4 hours, or overnight for the cleanest slices and best flavor. When ready to serve, cut into squares with a sharp knife, wiping the blade between cuts, and lift pieces out with a spatula.