Preheat oven to 350F. Spray a 13x9 inch pan with nonstick spray. In standard mixer, mix your cake mix, two eggs, one stick butter and 1 tsp. vanilla extract and spread carefully into bottom of pan.
Next mix in clean bowl soft cream cheese and beat until smooth about 1 minute, then add your other two eggs, other 1 tsp. vanilla until mixed well. Mix your powdered sugar with your cocoa and add to mixture then add other soft stick of butter beat until cream like frosting.
Spread evenly over batter in pan. Bake 35 to 45 minutes, but start checking it after 30 minutes. When cake tests done in center with toothpick it's done. Remove from oven . Sprinkle your dry powder/cocoa over the top of cake and let it cool.