Wash the pork thoroughly and cut it into small pieces. Season with salt and pepper, place in a bowl, and set aside. Remove the stems and seeds from the chiles, toast them, and soak them in hot water for 45 minutes.

Once the chiles are soft, blend them with the onion, oregano, cumin, garlic, vinegar, and olive oil. Pour this sauce over the pork and let it marinate in the refrigerator for two hours.

Cut the nopales into small cubes or thin strips. Boil them in enough water with salt. Once cooked, remove from heat, drain, rinse with cold water, and set aside.

Cut the aluminum foil or parchment paper into large squares, about 10 inches by 10 inches (25 cm x 25 cm). Place one or two pieces of pork, two tablespoons of nopales, a bay leaf, and a little butter on each square. Spoon some of the sauce over the top.

Fold the foil or paper tightly to form a pouch, tying it securely with kitchen twine so nothing leaks out. Place the pouches in a steamer and cook for two hours, checking the water level as needed. Once cooked, they're ready to enjoy.