Cream butter and cream cheese. Gradually beat in sugar and beat until mixed well. Add eggs one at a time, beating well. Combine flour, baking powder and salt. Add to creamed mixture and beat until blended. Stir in vanilla. Pour half of batter into separate bowl. Sift cocoa over half of batter and beat until blended. Pour half of chocolate batter into a greased and floured 9 X 5 inch loaf pan. Top with half of vanilla batter . Swirl batters together. Repeat layers and swirling. Bake at 350 degress for 45 minutes. Cover with foil and bake an additional 20 to 25 minutes or until done. Serve with ChocolateGravy.