Step 1: Using the tip of a paring knife, make a series of 1/4-inch-deep slits in the pork shoulder, 1 inch apart.
Step 2: Prepare the adobo: Stem the chiles, tear open, and remove the veins and seeds. Soak the chiles in water to cover until soft and pliable, about 30 minutes. Drain and place in a blender with the garlic, onion, oregano, cloves, allspice, cinnamon, salt, vinegar, and water. Puree to a smooth paste.
Step 3: Smear this paste all over the pork and let marinate for at least 4 hours, preferably overnight.
Step 4: Set up your grill for indirect grilling and preheat to 300 degrees F.
Step 5: Assemble the consommé: Place the onion, carrots, zucchini, pumpkin, cabbage, tomato, potato, corn, herb bundle, and water in a large low round pot—a Dutch oven is ideal. Or use an old pan or one whose outside appearance you don’t particularly care about.
Step 6: You’re now ready to assemble the barbacoa: Place the consommé pot in the center of the grill away from the heat. If your grill or smoker has enough headroom, place a metal rack, like a cake rack, on top and layer it with half the avocado leaves. Place the pork on top, fat side up, and carpet the pork with the remaining avocado leaves. (A Weber kettle grill outfitted with a rotisserie ring, which lifts the lid by about 6 inches, is ideal.) If you do not have a grill or smoker large enough to accommodate the height of the Dutch oven and the racked meat, carpet the consommé with avocado leaves and lay the pork shoulder directly on top. Top with more avocado leaves. (No rack needed.) Do not replace the lid of the Dutch oven. Add half the smoking chips to the coals. Tightly cover the smoker.
Step 7: Cook the barbacoa until the pork is fall-of-the-bone tender, 5 to 6 hours. Toss the remaining half of the wood chips on the coals after 1 hour. If using a charcoal grill, you’ll need to add 8 to 10 fresh coals per side every hour. When the pork is done, it will be fork-tender and the internal temperature will be about 180 degrees F.
Step 8: To serve the barbacoa, discard the top layer of avocado leaves and transfer the pork and bottom layer of leaves to a platter. Thinly slice the meat or cut it into chunks. Using a ladle, skim off any fat floating on the surface of the consommé. Stir in the chopped cilantro, chipotle, and salt and pepper to taste. The soup should be highly seasoned. Serve the consommé in bowls, the meat on a plate, both with warm tortillas and salsa.