Cook the whole piece of pork belly in a pot of boiling water for 8-10 minutes. Dish out and brush with thick soy sauce. Deep-fry in hot oil till the meat is golden brown.
Rinse the pork belly in cold water, then drain well and cut into thick slices. Soak mui choy for 30-40 minutes. Remove, rinse and drain, then chop finely. Put into a non-stick pan and fry briefly (to remove the moisture).
Heat oil and sesame oil in a saucepan. Fry shallots and garlic until fragrant. Add the meat slices and seasoning. Pour in stock and bring to a boil.
Put the prepared mui choy in a big stainless bowl. Transfer the pork slices and cooked seasoning to the mui choy and pour the gravy over. Steam the dish for 50-60 minutes. Dish out and serve.