Preheat oven to 350, grease 9x13 pan.
For the bottom layer, cream butter and 2 cups of sugar.
Add cocoa and 4 eggs.
Mix thoroughly on low speed.
Add 1 cup flour and 1 tsp vanilla, mixing again.
Pour into pan.
For the top layer, in a clean bowl mix cream cheese and 1 1/2 cups sugar on high until smooth.
Add 5 eggs and mix on low speed.
Add 1 1/2 teaspoons vanilla, 1/2 cup flour mix again.
Pour this over chocolate layer, swirling a bit to give it a zebra effect.
Bake 45 - 55 minutes or until center sets.