Preheat the oven to 375°.
In a large sauté pan, heat oil over medium to high heat until very hot but not smoking.
Dry the meat with paper towels, rub it all over with the white pepper, sprinkle it with the salt, and brown well on all sides. Remove from the pan and set aside.
Pour off the fat or add oil to the pan as needed so you have a total of about two tablespoons in the pan. Add the onions and cook, stirring occasionally, until translucent. Add the garlic, ginger, and chili and cook stirring for one minute. Add the soy sauce, vinegar and dry sherry. Bring to a simmer, stirring to scrape up any browned bits in the bottom of the pan.
Place the pork shoulder in a Dutch oven or a pot with a cover. Pour the liquid over the pork. The liquid should come about halfway up the sides of the pork shoulder; if it does not, add some water or chicken stock. Place all other dry ingredients in the Dutch oven and bring the liquid to a simmer. Skim any film from the top, then cover. Place in the oven, and cook until the meat is tender, 2 to 2½ hours. To check for doneness, plunge a fork straight down into the pork and try to pull the fork out. If the fork slides out easily, the pork is done. If the pork hangs onto the fork, give it more time in the oven. When the pork is done, remove it from the liquid, cover it loosely with foil, and set aside.
Place the pot on the stove over medium heat. Simmer to reduce the braising liquid to intensify the flavor. For a thicker sauce, reduce it until it coats the back of a spoon. Finish the sauce by adding the hoisin sauce to taste.
Serve pork shoulder over jasmine rice and steamed bok choy.