Prepare the marinade: Scorch onions and garlic with skin on until golden brown on all sides. Remove and blend with rehydrated ancho and arbol chiles, some cooking liquid, salt, and pepper until a thick texture suitable for coating the pork loin.
Marinate the pork loin: Place pork loins in a dish and coat thoroughly with the marinade on all sides. Ideally, marinate overnight for deeper flavor penetration.
Prepare the clay oven dough: Mix traditional clay soil with salt and water gradually to achieve a dough-like texture that can cover the pork loin without being too runny.
Prepare vegetables and wrap pork: Place basic vegetables such as leek, carrot, and onion with a little salt as a moisture and flavor base. Lay banana leaves on top, place the marinated pork loin, and wrap tightly. Tie securely to keep shape.
Assemble and bake in clay oven: Place the wrapped pork loin on the vegetable bed on a griddle or heatproof base. Cover completely with the clay dough, sealing all holes to prevent heat escape. Preheat oven and cook slowly at low heat for approximately 3 hours.
Prepare pickled vegetables: In a pot, combine equal parts alcohol vinegar and water with garlic, pepper, hot peppers, and sugar. Bring to boil, then add sliced onion and carrot. Cook for 5 minutes for softer pickles or cool immediately for crispier texture. Store in a jar.
Make whiskey-ketchup sauce: In a frying pan, heat oil and add garlic until fragrant but not browned. Add a shot of whiskey and let alcohol evaporate. Add pork cooking liquid to enhance flavor and reduce. Finish by mixing in ketchup base and stir well.
Rest and serve: Remove pork loin from clay oven and let rest to retain moisture. Slice and assemble sandwiches with bread rolls, pork loin slices, pickled vegetables, and whiskey-ketchup sauce.