This is a great question. It is traditionally made with pork loin, but traditionally, pork was not bred to be as lean as it is today. So the pork loins of yesteryear had more fat in them, which is what you want. Look for pork loin that has been sustainably raised from a small producer, perhaps a heritage pig. This pork will be more like the cuts of pork loin used to make this dish in Italy, and you will get a very tender braised pork dish. Commercially raised pork might end up being on the drier side. You can also use a small pork shoulder instead of a loin, which will have a generous amount of fat. If you go that route, you may need to let the sauce sit at the end and skim off any excess fat that rises to the top before serving or pureeing the sauce.