Take a pork shoulder. Rub a paste made out of an onion, ten cloves of garlic, some red wine vinegar, salt, black pepper (ground and peppercorns), cumin and chili powder onto it, poke some holes, and park it in a bag in the fridge overnight
the next day, pop it on a roasting rack, put a little water in the bottom of the pan, and roast at 300, turning once an hour until it's done. mine took five hours.
it's mostly mark bittman's recipe.