'Doctor' up the cake mix by using milk instead of water and melted butter instead of oil. Bake in a 9X13 pan according to the packages directions.
While the cake is baking, combine the butter, powdered sugar, milk, vanilla and crushed Oreos. Mix until well combined.
Pour the can of sweetened condensed milk in and combine with the Oreo mixture. The consistency should now be pourable. Set aside until the cake has finished baking.
Once the cake has finished baking, remove from oven and let the cake rest for 5 minutes.
Using the back of a wooden spoon, poke holes in the cake. I usually go back and forth creating rows until the entire cake has been poked.
Pour the cookies and cream 'filling' over the cake and spread to cover the entire cake.
Let cool completely. (there will be a layer of the filling left onto of the cake that hardens like icing.)
Once the cake has cooled completely, spread the cool whip (or homemade whipped cream) onto the cake and garnish with crushed oreos.
To make homemade whipped cream: whip 1 1/2 cups whipping cream, 1/3 cup sugar and 1/2 tsp vanilla together until stiff peaks form.
Refrigerate for at least 1 hour before serving.