Boil the pork hock in enough water to cover for 20 minutes. Drain, rinse, pat dry, and season with salt.
Soak the shiitake mushrooms in warm water until soft. Drain, squeeze out any excess water, and trim the stems (if needed).
Sear the pork in a little oil over high heat until lightly browned.
Sauté the mushrooms until lightly browned. Add the garlic and onion, then cook until softened and fragrant.
Return the pork to the pot. Add the soy sauce, Shaoxing wine, brown sugar, and 1½ cups water (for pressure cooker).If cooking on the stovetop, use 4 cups water instead.
Add the star anise, bay leaves, cinnamon stick, and black pepper.
Cook on high pressure for 45 minutes to 1 hour for cut-up pieces, or 1½ to 2 hours for a whole hock.If cooking on the stovetop, simmer over medium-low heat for 2½ to 3 hours. The pork should be very tender and easy to pull from the bone. Taste and adjust the sauce as needed.
Transfer the meat to a serving platter. Mix the cornstarch and water until smooth, then stir into the sauce. Add the sesame oil and simmer until slightly thickened.
Blanch the bok choy for 30 seconds to 1 minute, or add it straight to the sauce and let it wilt.
Arrange the bok choy around the meat, then spoon the sauce over the top.
Notes
Pork hock: From the lower leg, sometimes with the feet or trotters. Cut-up pieces cook faster and absorb more flavor.
Shiitake mushrooms: Dried has more flavor, but fresh works too. Dried banana blossoms are another option.
Soy sauce: Use regular soy sauce and a little bit of dark soy sauce for color.
Shaoxing wine: Adds more flavor to the sauce. Use cooking wine or a little pineapple juice if needed. Rice vinegar also works.
Bok choy: Shanghai bok choy, pechay, or napa cabbage all work. Carrots or chayote are also nice for more vegetables.