Preheat oven to 400degreesF. Hamburgers: Mix first 6 ingredients and press into an ungreased 10 by 15 inch jelly roll pan. Prick with a fork. Bake for 10 minutes. Drain off juices (if there's a lot of excess). Cool. Cut into 24 squares. Place squares on dinner rolls. Combine mustard and ketchup and spread on rolls. Top with pickles and cheese, if desired. This makes 12 servings of 2 hamburgers each.