Place onions in a Dutch Oven or large saucepan. Place corned beef on top of onions. Add peppercorns, bay leaves and cloves. Cover with water. Bring mixture to a boil. Reduce heat to medium and let simmer until beef is tender, about 3 1/2 hours. As the corned beef cooks, remove any scum that accumulates on top. Remove corned beef. Add carrots, cabbage and potatoes. Bring vegetables to a boil. Simmer on low for 20 minutes until vegetables are tender. Slice the corned beef across the grain into thin slices. Serve corned beef with vegetables and some cooking liquid. Serve with hot mustard or horseradish sauce.
Corned Beef and Cabbage was a traditional dish served in rural Ireland. Corning is a form of curing. The name comes from the Anglo-Saxon times before refrigeration. Pellets of salt, the size of corn, was rubbed into the beef to keep it from spoiling and to preserve it. Today, brining in salt water is the traditional method of curing.