01 -
Preheat oven to 350°F (175°C).
02 -
Grease a 9 x 13 inch baking pan or dish with cooking spray.
03 -
Arrange the Oreo cookies in a single layer at the bottom of the baking dish.
04 -
Evenly pour the sweetened condensed milk over the layer of cookies.
05 -
Spread the whipped topping over the cookie and condensed milk mixture.
06 -
Sprinkle the dry chocolate cake mix evenly over the top.
07 -
Arrange the sliced butter on top of the dry cake mix, then sprinkle the chopped Oreos over the top.
08 -
Bake the dish in the preheated oven for 35 to 40 minutes.
09 -
Serve hot, topped with ice cream and chocolate sauce, if desired.