In a heavy pot over medium-high heat, saute the onions in butter until they're beginning to turn brown
Set chuck roast on top of the onions. Add all remaining ingredients. Cover the pot and simmer (over low heat) on the stovetop for 6 hours, or until beef is fork-tender and falling apart. ((If the meat isn't tender yet, keep simmering)
Shred meat until all large chunks are gone. Serve immediately or continue to simmer for 30 minutes to 1 hour.
(The meat can be refrigerated overnight. Remove the hardened fat from the top of the pan before re-heating)