Preheat oven to 350 degrees.
Mix the cake mix, melted butter and 2 eggs together.
Spray the sides and bottom of a 13 x 9 inch pan with non stick spray.
Pat mixture evenly into the bottom of the pan.
With an electric mixer, mix cream cheese, remaining eggs, and vanilla together.
Gradually add the powdered sugar (saving some to sprinkle on top) and blend until smooth.
Pour over chocolate layer.
Bake for 45 minutes.
The edges and most of the top will become a golden brown and begin to slightly pull away from the sides of the pan.
The top layer will remain somewhat "gooey".
As soon as you remove it from the oven, sprinkle generously with the remaining powdered sugar.