Wikipedia
Pernil (pernil asado, pernil al horno, roast pork butt), a slow-roasted marinated pork shoulder, In Puerto Rico the dish is commonly shared during Christmas, typically accompanied by arroz con gandules (rice with pigeon peas).
The pork shoulder is used as a whole piece, with skin and bone. It is marinated the day prior to roasting with sofrito, salt, pepper plus possibly additional spices ( oregano, adobo). Sofrito are placed deeply within the meat through small cuts. After marination the covered meat is slowly roasted initially in the oven for several hours, and, in the final phase, at a higher temperature with the cover off to get the skin crispy. When finished, the meat “falls off the bone”, and the crispy skin (cuero) is separated, cleared of fat, and can be served separately as cueritos (skin chips). A typical pernil serves about 8 people.
Left over meat from a pernil can be used in a Cuban sandwich.