Rinse the pork leg well and scrape off visible hair with a knife. If the hairs are too stubborn, use a kitchen torch to scorch them then scrape clean with a knife.
Place the pork leg and knuckles in a pot, cover with water and boil hard for 10 minutes.
Rinse the pork and scrape off any impurities attached to it.
Place the pork in a clean pot. Add all the ingredients except the fish sauce. Bring to the boil, lower the heat, cover and simmer until the meat falls off the bone.
Taste the broth every half hour or so and add fish sauce and sugar, as needed. DO NOT be tempted to add more soy sauce to prevent the stew from turning too dark.
When the pork leg is done, leave to soak in the broth until cool.
Scoop out the pork, pull off the bone and discard. Cut the meat and skin into slices.
Pile the sliced pork leg over rice, drizzle in a some of the broth (strain and reheat the broth for best results) and serve with pickled mustard greens on the side.
Alternatively, arrange the pork slices over noodles, add blanched mung bean sprouts and Chinese broccoli on the side and ladle in the strained and reheated broth.