Combine everything (except for the pork and the hoisin sauce) in a food processor and process to a thin paste. Pour over the pork and mix, ensuring that all surfaces of the pork get some marinade on them. Allow to marinate in the refrigerator overnight.
Place pork, any residual marinade, and some water in your pressure cooker (use the minimum amount of water for your pressure cooker -- for my ancient 6-quart cooker it's 1 cup). Bring to pressure, cook 15 minutes, then allow 20 minutes natural pressure release.
Remove pork from pressure cooker. Some meat may have fallen off the bone, some may still be on the bone, make sure you don't miss any of it. Place in a single layer on a foil-lined baking tray, baste with hoisin sauce, and broil for 2 minutes. Remove from the oven, re-baste with more hoisin sauce, place back in the broiler, and broil another 2 minutes. Broiler temperatures vary, so check often to ensure that nothing's getting burnt.