This is delicious - you can use chuck roast or pork shoulder.
chuck roast or pork, fat trimmed (I've done anywhere from 3-6 lbs)
onions, sliced (I used 5 large for 6 lbs meat)
garlic, peeled, left in whole cloves (I used ~10 cloves for 6 lbs. meat)
small amount peppercorns
beef stock, enough to fill crock halfway up meat
Place onions in bottom of crock; add meat, garlic and peppercorns. Pour in stock, cover, and cook on low 8-12 hours or until meat falls apart when forked.
Remove meat, separate fat and shred. Pour liquid through sieve and let fat rise; spoon off fat. (I put mine in the fridge for a while until the fat hardens and it's easier to remove.)
Serve on crusty rolls with onions and juice for dipping.