1. For the adobo: In a blender, combine allspice berries, ancho chile, garlic, white onion, white vinegar, avocado leaf, lard, salt, guajillo chile and cumin. Blend until smooth and set aside.
2. Preheat grill for 45 minutes before using. Once hot, sear pork over direct heat and season with salt and pepper. Remove from grill and set aside.
3. Pour adobo over pork, let marinate for half an hour, and set aside. On a chopping board, place aluminum foil and banana leaves. Top with marinated pork and wrap tightly to keep from spilling.
4. Return to grill and cook over direct heat for 1 hour, until the temperature reaches 170 °F, or until cooked thoroughly. Remove from grill and let rest for 20 minutes.
5. Serve grilled pork barbacoa with onion, cilantro, and salsa.