Put half of onions in bottom of crockpot. Then add meat and other ingredients with remaining onion on top. Cover and cook over night or for 8 to 12 hours on low. Remove bone and fat from meat. Put meat back in crockpot. Add chopped onion and barbecue sauce. Cover and cook for an additional 8 to 12 hours on low, stirring 2 or 3 times. Serve from crockpot on large buns.