Stuffed vegetables were a speciality of my grandmother, who made them often for her delicious family meals. This basic pork stuffing works well with dried mushrooms, as well as bitter melon, eggplant and medium-hot fresh chillies.
It's best to start soaking the mushrooms the day before. Good dried mushrooms have large, thick caps that need time to hydrate fully, or else you will have a hard, dry part in the centre. If you can afford them, buy dried "flower mushrooms" - a type of shiitake with an attractive pattern of white cracks on the dark surface of the cap.
It can be difficult to judge the number of mushrooms you need for this amount of stuffing. If you have extra soaked mushrooms, thinly slice them and add them to the dish as the ingredients are simmering. If you have extra stuffing, shape it into meatballs and brown them briefly in the hot fat, before cooking with the other ingredients.
Rinse the mushrooms briefly, then put them in a large bowl and add enough tepid water so that they can bob around. Leave them to soak for about eight hours or until fully hydrated, turning them over once or twice to soak evenly. Squeeze the mushrooms to remove excess water, then cut off the stems as close as possible to the cap.
Strain the soaking liquid through a fine sieve placed over a bowl. Measure out 150ml (⅔ cup) of the soaking liquid into one bowl, add the oyster sauce and stir to dissolve. Measure out 60ml (¼ cup) of soaking liquid and pour into another bowl, add two teaspoons of cornstarch and stir to dissolve.
Put the minced pork in a bowl and add the soy sauce, rice wine, sesame oil, sugar, salt, white pepper and two teaspoons of cornstarch. Mix thoroughly. Finely mince the spring onions and chop the 10 grams of coriander, add them to the bowl and mix again. If you have time, refrigerate the mixture for about an hour.
Place the mushrooms cup side-up a tray. Add a spoonful of the stuffing to each, pressing down so it is packed into the mushroom cap and mounded over it slightly. Heat a wide skillet over a medium flame and when it’s hot, add about 15ml (1tbsp) of cooking oil. Swirl the oil in the pan so that it’s lightly but evenly coated. When the oil is hot, add the stuffed mushrooms, meat side down. Lightly brown the top, then turn the mushrooms over. Pour the oyster sauce soaking liquid mixture into the skillet around the mushrooms. Bring the liquid to a boil then lower the heat, cover with the lid and cook at a low simmer for about 10 minutes, or until the meat is cooked through.
While the mushrooms are cooking, bring a large pot of water to the boil. Cut the iceberg lettuce into wide strips. When the water boils, add the lettuce and stir. Cook for about 30 seconds, or until the lettuce wilts. Drain thoroughly, then wrap the lettuce in a clean, dry kitchen towel and squeeze out as much liquid as possible. Arrange the lettuce in a wide, shallow bowl.
When the mushrooms are cooked, use tongs to take them from the skillet and arrange them over the lettuce. There should be at least 120ml of liquid in the skillet (if not, add some of the excess soaking liquid). Heat the liquid until bubbling over a low flame. Stir the cornstarch and soaking liquid mixture and immediately add it in a stream to the liquid in the skillet. Stir constantly, and add just enough so the liquid forms a very light sauce; you might not need all of the cornstarch. As soon as the liquid in the skillet simmers again, turn off the heat.
Pour the sauce over the mushrooms and lettuce, then garnish with fresh coriander sprigs before serving with vegetables and steamed rice.