"If you have grown up, lived, or traveled to the Midwest, this recipe is from a popular restaurant that was in Lincoln, NE. I've been told it's an acquired taste, but having grown up on them, I love them! It's a loose meat sandwich. Use a slotted spoon to portion out the meat. Serve on buns with mustard and sliced dill pickles."
Combine ketchup, salt, mustard, horseradish, Worcestershire sauce, and ground black pepper in a 1-cup measuring cup. Add more ketchup if combined ingredients don't equal 1 cup. Stir until well mixed. Place ground beef in a stock pot; pour ketchup mixture over the ground beef.
Fill the same measuring cup with warm water. Stir to loosen any fine seasoning remaining; pour into stock pot. Stir onion into ground beef mixture; add monosodium glutamate. Mix until ingredients are well combined.
Cook and stir the ground beef mixture over low heat until the ground beef is finely crumbled, about 15 minutes. Bring to a boil; cook until flavors blend, about 25 minutes.