Place the pork butt in a large baking dish. Wearing rubber gloves, rub the chorizo seasoning into the pork on all sides. Cover and refrigerate overnight.
Preheat the oven to 350 degrees F. Tie the meat with butcher's twine and let sit at room temperature for 30 minutes.
In a braising pan or Dutch oven, heat the oil over medium-high heat. Add the meat and brown on all sides, 5 minutes. Remove from the pan. Add the onions, salt, and pepper, and cook, stirring, until soft, about 3 minutes. Add the garlic and cook, stirring, for 30 seconds. Add the tomato paste and bay leaf, and cook for 1 minute. Add the wine. Stir to deglaze the pan and until reduced by 1/2. Add the potatoes, carrots, sweet potato, and parsley. Return the meat to the pan and add enough chicken stock to cover the vegetables.
Cover tightly and place in the oven. Roast until the vegetables and meat are tender, and the meat registers 160 to 165 degrees F on an instant-read meat thermometer, 2 hours. Remove from the oven. Remove the pork from the pot and cover loosely to keep warm, and let rest for 10 minutes before carving. (The final temperature of the meat after resting for 10 minutes or so may read 170 to 175 degrees F.)
Serve with the vegetables and pan juices, cooked green beans and hot bread.
Yield: 4 servings