Place all ingredients except chocolate chips and sponge cake, if using in a large blender. Make sure the blender can chop ice. Blend on high for 1 minute or until it is the texture of soft serve ice cream. Eat immediately or place in a freezer container and freeze 30-45 minutes for a firmer texture. This recipe is designed to be eaten the same day. If frozen overnight it will freeze solid. This recipe can also be cut in half.