Although I have not tried this myself yet, I have heard from many others that it is positively wonderful!

Neiman Marcus Cake

Cake mix (can use yellow, white, chocolate, etc)
2 eggs
1/2 cup butter
nuts and/or semi-sweet chocolate chips (optional)

1 box cream cheese
1 box powder sugar
2 eggs

Mix the first three items together and pat down in a greased cake pan (9x13). Sprinkle the top with nuts and/or chocolate chips. Mix the remaining ingrediants and spread on top. Cook at 350 for about 40 minutes.