From: Fuchsia Dunlop - Food of Sichuan
Cut the pork into very thin slices and then cut evenly into thin strips, ideally 1¼ inches (3-4mm) thick (you can chill the pork for an hour or so in the freezer beforehand to make cutting easier).
Place the strips in a bowl, add 1 tbsp cold water and all the marinade ingredients except the oil. Stir in one direction to combine, then set aside while you prepare the other ingredients.
Rinse the preserved mustard tuber thoroughly and cut it into very thin slices to match the pork. If it is extremely salty, blanch it for 10 seconds in boiling water, then drain.
Cut the scallions into 2½-inch (6cm) lengths and lengthwise into fine slivers.
Combine the sauce ingredients with 2 tbsp cold water in a bowl.
Add the 2 tsp oil to the marinating pork and mix well, then heat the 4 tbsp oil or lard in a seasoned wok over high heat.
Add the pork slivers and stir-fry until they have separated and are turning pale, then add the preserved vegetable and continue to stir-fry until the pork is just cooked and the preserved vegetable is fragrant.
Give the sauce a stir and add to the wok, stirring swiftly as it thickens.
Finally, add the scallions and stir once or twice to give them a lick of heat. Serve.
