Place fresh apple chunks in a 8″ x 8″ pan. Cover with 2 cups of apple sauce (hold ½ cup in reserve), sprinkle with sugar (optional), and dot with butter or margarine. Place in 375°F oven to begin heating. In a separate bowl, combine flour, baking powder and salt. Cut in shortening. Combine the ½ cup apple sauce with the egg yolk. Add to flour mixture. Mix well. Drop soft dough evenly over top of apple mixture. Bake at 350°F for 40 minutes or until golden brown.