Place the beef in a crock pot. Spread Mustard over beef as a binder. Mix the rub items together and coat the beef.
Mix the broth and liquid smoke. Pour around the beef but don't disturb rub. Cut 4TBS butter into pats and cover roast. Cook on low 8hrs, or high 4hrs.
Finely dice the onion and mince the garlic. Cook in remaining butter slowly so to not caramelize, but sweat. Mix remaining ingredients and add to pot, simmer.
When beef is done, drain brine from pot and shred beef. Add warm sauce and mix with beef. Simmer on low in crock pot for 30 mins. Serve.
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