In a large pot of boiling water, add scallion, ginger, bay leaf, and peppercorns.
Add the pork shank simmer for thirty minutes.
Remove pork shank from water and pat dry.
Fry:
Heat oil to 375 F (190 C) in a large pot or wok.
With a small knife, puncture the skin of the pork shank completely and uniformly.
Baste the pork shank with soy sauce, being sure to thoroughly rub into the pierced skin.
Fry the pork for five minutes or until the skin is crispy and dark. Remove and drain.
Braise:
Preheat oven to 350 F (175 C).
In a braising dish, boil water, soy sauce, oyster sauce, brown sugar, star anise, and vinegar.
Add the blanched and fried pork shank to the liquid.
Cover, then transfer dish to the oven. Braise shank in the oven for three hours or until the meat falls off the bones.
When finished, remove the pork shanks from the braising liquid and keep warm.
To serve:
Heat the braising liquid over medium-high heat to a simmer.
In a small bowl, make a slurry with cornstarch and water, stir the slurry into the simmering braising liquid, and continue stirring until the sauce is thick and glossy.
Serve warm pork shank with sauce, warm bok choy, and shiitake mushrooms (optional).
