Preheat oven to 350 degrees and prepare 10"X13" pan with non-stick spray. In a large bowl, mash slightly with a fork the black beans with the liquid from the can, leaving about half of the beans intact. Add the applesauce and cake mix. With an electric mixer, mix the ingredients for about 3 minutes on medium speed. Batter will be thick. Pour into the prepared pan, add optional chocolate chips to the top of cake and bake for 35-40 minutes. Test with a toothpick, if still wet, cook for another 5-10 minutes. Cool completely. Makes 16 pieces.