Take the pork shoulder and slash the rind with a sharp knife into diamond shapes. Stab the meat all over.
Put remaining ingredients in a food processor and process until blended but still slightly chunky.
Smear the seasoning mixture all over the meat, working it into the slashes you have cut.
Place the meat into a slow cooker. Put any remaining seasoning mixture on top of it. Cover.
Cook for 8 hours on Low.
Pull off rind and fat - discard. Pull meat into chunks and shreds for serving. Moisten with the broth in the pot.