Cut pork crosswise into 4 slices. With a meat mallet, pound each pork slice between plastic wrap to 1/4-inch thickness.
In a shallow bowl combine flour, onion or garlic powder, and pepper. In another shallow bowl combine egg and milk or water. In a third bowl place crushed crackers or bread crumbs. Dip each pork slice into the flour mixture, coating well, then into the egg mixture, and then into the crumbs to coat.
In a large skillet cook 2 pork slices in hot oil over medium heat for 6 to 8 minutes or until pork is done, turning once. (Or cook on a well-greased griddle.) Remove from skillet; keep warm. Repeat with remaining slices, adding more oil, if necessary.
Place on buns. If desired, serve with mustard, catsup, onion, pickle, and/or peppers. Makes 4 servings.