Marinating: Combine marinade ingredients in bowl large enough to hold pork, mixing well. Add pork, cover, and marinate at room temperature for 1 hour. Braising: Drain pork, taking care to remove pieces of garlic. Heat oil in wok until it begins to smoke. Fry pork cubes, a few at a time, until brown and crusty. Do this quickly to sear meat without cooking it through. Drain in Chinese strainer or on paper towel. Strain and reserve cooking oil. Clay Pot: In cool clay pot, combine water, bean sauce, dark soy, minced ginger, dried orange peel, and sherry. Bring to boil, then add braised pork cubes. Reduce heat, cover pot, and simmer for 30 minutes. Meanwhile, wash and trim green onions, cut into 5 cm sections. Drain oysters. When pork has simmered 30 minutes, add onions and oysters. You can stop the dish before adding oysters and onion. Cover and cook at medium heat for 15 minutes more. Turn up to boil, dribble in cornstarch paste to make light gravy. Serve with garnish of parsley.