lard
It’s my understanding that the meaty chunks we associate with carnitas are cooked similar to a confit- braised in its own rendered fat (lard) low until the collagen is broken down then crisped. By the way, that does answer the question about how something can be braised and crispy on the outside at the same time. Since the outside is in contact with fat only then then it will essentially dehydrate.
However, this has all been pieced together from various sources so I’ve honestly never been sure if this technique is universal or if there even is a universal technique. I mean, this works great for high collagen, high fat cuts like shoulder but the resulting product is different than trompa or chicharron (which itself has different subtypes).
All of which is to ask, is there an agreed upon definition for carnitas? The literal translation (“little meats”) is so fundamental is it actually one dish or an umbrella term for the result from cooking a whole pig? Do meats like chicharron fall under the definition of carnitas?
You describe a low then high cook. In Taco Chronicles, they specifically describe it as high then low.
So it seems that at best, the method is not universal. Same difference as a traditional sear vs reverse dear I suppose.
There are many different ways to cook carnitas: braise in lard and serve soft, braise in lard and serve crisp, braise in other things and serve soft. Could be just shoulder or some other braising cut or could include all different parts.
One of Diana Kennedy’s books has a great recipe for carnitas caseras that includes a whole orange.