Preheat oven to 350ºF.  Cream margarine and cheese. Gradually add sugar, beating at medium speed with an electric mixer until fluffy. Add egg, egg whites, and vanilla, beating well. In a small bowl, sift together flour and baking powder. Gradually add to creamed mixture, mixing well. Divide batter in half. Sift cocoa over half of batter and fold in gently. Spoon cocoa mixture into an 8 inch square baking pan coated with non stick vegetable coating. Pour remaining half of batter into pan. Cut through the mixture with a knife using an "s" motion to create a marble effect. Bake for 25 minutes or until done. (Test for doneness with a toothpick in the center of the brownie. if the toothpick comes out clean, the brownies are done.) Cool in pan on wire rack. Cut into 10 brownies. Makes 10 servings, 1 brownie each. 1 brownie = 1 grain and 1 fat exchange.