In a small bowl, combine the soup, mustard, Worcestershire sauce and horseradish. Set aside. In another bowl, lightly beat the egg.
Add the bread crumbs, onion, salt, pepper and 1/4 cup of the soup mixture. Crumble beef over mixture and mix well. Shape into six patties.
In a large skillet, brown the patties in oil; drain.
Combine remaining soup mixture with water; pour over patties. Cover and cook over low heat until meat is no longer pink and a thermometer reads 160°, 10-15 minutes.
Remove patties to a serving platter; serve sauce with meat.