How to Make It
Score the skin of the pork with a sharp knife. Season the pork with 2 teaspoons salt and 1 teaspoon pepper. In a 5-to 6-quart crock pot, heat the oil over high heat until hot. Sear the pork butt, turning once, until browned, 6 to 8 minutes total. Transfer the pork to a plate. Cook the garlic and onion in the fat in the crock pot, stirring occasionally, until golden, about 6 minutes. Stir in the tomatoes, water, chipotles, oregano, and cumin. Then add the pork with any accumulated juices and cover the crock pot.
Simmer the pork butt on low, covered, turning over once, until the meat is very tender, 7 to 8 hours. Shred the pork, discarding the bone, then place the shredded pork back in the cooking liquid, breaking up the tomatoes with a spoon. Season with salt and pepper to taste and serve with cilantro, avocado and tortillas.