Prepare the chocolate cake mix according to the package instructions and bake it in a baking pan.
Once the cake is baked, let it cool for a few minutes and then poke holes in the top with a fork.
Mix the sweetened condensed milk, cookies and cream pudding mix, and whole milk until smooth. Pour this mixture over the cake, ensuring it fills the holes.
Spread the whipped topping over the cake and sprinkle crushed Oreos on top. Refrigerate for a few hours before serving.
Notes
This cake is best served chilled. You can add more crushed Oreos for extra crunch.