Preheat oven to 350°F; grease a 9×13-inch baking pan with cooking spray
For the crust: In a medium bowl, combine cake mix, 1 stick of melted butter and egg in a mixing bowl. Mix ingredients together using on low for 2 minutes.
Evenly spread the batter in the bottom of the pan
For the filling: Using the same mixing bowl, add the cream cheese and beat on low until smooth.
Add eggs, 1 stick of melted butter, powdered sugar, and vanilla extract then mix on a medium speed until incorporated and smooth
Place 1 cup chocolate chips into a microwave safe bowl or dish.
Microwave chips on high for about 30 seconds then take out and stir. Continue microwaving in 15 second intervals until fully melted
Measure out 1 cup of the cream cheese filling. Combine cream cheese filling with melted chocolate. Whisk together until well blended and all one color.
Pour filling on top of crust and spread out evenly.
Dollop the chocolate filling on top of the cream cheese filling
Using a tooth pick swirl around the filling to create a marble appearance
Bake for 45 minutes. Then once out of the oven cool for 30 minutes.