3 1/2 lb boneless pork shoulder, trim away fat and cut into fourths
2/3 cup Worcestershire sauce
1/2 cup ketchup
1/4 cup firmly packed brown sugar
1/4 cup tomato paste
1 medium onion, chopped
2 tbsp prepared mustard
2 tbsp vinegar
Using a 6-quart crockpot or other slow cooker, combine the Worcestershire sauce, ketchup, brown sugar, tomato paste, onion, mustard, and vinegar in the cooker. When the sauce is well mixed, add the pork. Stir to cover the pork.
Place lid on cooker and cook on low setting 8 to 10 hours.
Remove pork to a cutting board and using two knives, shred the pork. Return the meat to the cooker and stir into the sauce.
To serve, place about a fourth of a cup on each sandwich bun and serve with the condiments of your choice.