1. Preheat oven to 350 degrees and line baking pan with parchment paper.
2. Combine cake mix, eggs and oil. Dough will be thick.
3. Press into a 9X13 pan (or use half of a regular sheet pan, the dough won't spread) (or you can use two loaf pans!)
4. Bake for 10-15 minutes! These will be fudgy cookie bars!
5. Let cool in pan.
6. Filling: Beat butter and cream cheese until smooth. Add vanilla extract and 2 cups powdered sugar. Continue to add sugar until you reach your desired sweetness. Remember that the chocolate layers will be sweet so the filling can be less sweet to balance it out.
7. If you baked your dough on one pan, cut the bake in half and frost one on the halves. Then place the other side of the bake on top to sandwich the two together with your layer of cream cheese filling in the middle.
8. Let chill in the fridge for at least 20 minutes and then cut into bars. These are very rich, so I recommend small slices! I also recommend serving them cold!