This dish was my grandmother’s speciality: something she made only on special occasions, such as Lunar New Year, when she cooked for at least 30 people. What separates a good version of the dish from a great one is the knife-work: the dried oysters and vegetables must be hand-chopped as finely as possible. Don’t use a food processor, or the results will be coarse, not refined.
The oysters and mushrooms need to be fully hydrated, which can take several hours. I start soaking them the night before.
This dish is usually served with hoisin sauce, but try it without first - the delicate, complex flavour can be overwhelmed by the strong, sweet sauce.
Rinse the dried oysters and mushrooms then put them in a bowl, cover with warm water and leave to soak for several hours, or until fully hydrated. Take the mushrooms from the water and squeeze them to remove the excess liquid. Remove and discard the stems from the mushrooms, then cut the caps into 5mm (¼in) pieces. Squeeze and discard the liver (which is soft and greenish-grey) from the dried oysters and rinse them well, then cut them into 5mm (¼in) pieces. Put the oysters and mushrooms in a bowl. Pour the soaking liquid through a fine sieve to remove any sediment.
Peel the water chestnuts then rinse them thoroughly. Cut the water chestnuts, celery and bamboo shoots into 5mm (¼in) pieces, keeping the ingredients separate. Bring a pot of water to the boil, add the bamboo shoots and simmer for five minutes before draining.
Put the minced pork in a bowl and add the soy sauce, rice wine, sugar, salt, white pepper and one teaspoon of cornstarch. Mix well and leave to marinate for about 15 minutes. Dissolve the oyster sauce in 60ml (¼ cup) of the oyster and mushroom soaking liquid.
Place a wok over a high flame and when it's hot, pour in 15ml (1tbsp) of cooking oil. Add the celery and bamboo shoots and stir-fry for two minutes. Add the water chestnuts and stir-fry for a minute, then mix in the oysters and mushrooms. Cook for another minute, stirring often, then transfer the ingredients to a bowl. Put the wok (no need to wash it) back over a high flame and add 10ml (2tsp) of cooking oil. When the oil is hot, add the pork and use a wok spatula to break it into very small pieces. Stir-fry until the pork loses its pink colour, then add the vegetable and oyster mixture back to the wok and mix well. Add the oyster sauce/soaking liquid mixture and stir well. Lower the flame, cover the wok with the lid and simmer for about three minutes, stirring often. Taste the mixture and add a little salt and/or oyster sauce, if necessary.
Dissolve the remaining two teaspoons of cornstarch in 30ml of the soaking liquid and mix into the ingredients. Turn the flame to high and stir constantly. The sauce should lightly coat the ingredients; if it's too dry, add more soaking liquid, if it's too wet, stir constantly over a high flame until the sauce is reduced slightly.
Cut the spring onions into 5mm (¼in) pieces and stir them into the mixture. Stir in the sesame oil, then transfer the ingredients to a serving dish. Serve with iceberg lettuce cups and small bowls of hoisin sauce.
To eat, scoop the mixture into iceberg lettuce cups that have been smeared (if you like) with a small amount of hoisin sauce.