In a large bowl, combine the egg, milk, cheese, breadcrumbs and salt. Add the ground beef, mixing well, and form this mixture into six to eight miniature meatloaves. Place these in a lightly greased 9x13 inch baking dish.
In a separate small bowl, combine the ketchup, brown sugar and mustard. Stir thoroughly and spread over each meatloaf.
Bake, uncovered, at 350 degrees F (175 degrees C) for 45 minutes.