Preheat oven to 350°
Spray a 9x13 baking dish with cooking spray, set aside.
In bowl, stir together cake mix, ½ cup butter (1 stick), melted and 1 egg until smooth.
Press mixture into the bottom of your prepared pan.
In bowl of stand mixer beat cream cheese, vanilla and powdered sugar together until smooth. Remove half of the mixture from the bowl and reserve for later (eyeball it). In the remaining cream cheese mixture, add cocoa powder, ¼ cup butter, melted and remaining egg. Beat until smooth.
Spread this mixture over top the cake mix layer. Bake for 30 minutes until just set.
Allow to cool completely.
When base is completely cool, stir in half of your chopped Oreos to the remaining cream cheese mixture. Then fold in thawed Cool Whip until smooth.
Spread this all over your cooled base. Sprinkle with remaining chopped Oreos.
Chill for at least an hour. Cut into squares when ready to serve.