1 pound 5 ounces (600g) eggplants (1–2 large)
Cooking oil, for deep-frying
1 1/2 tablespoons Sichuan chile bean paste
1 1/2 tablespoons finely chopped garlic
1 tablespoon finely chopped ginger
10 tablespoons (150ml) hot stock or water
4 teaspoons superfine sugar
1 teaspoon Chinese light soy sauce
3/4 teaspoon potato starch, mixed with 1 tablespoon cold water
1 tablespoon Chinkiang vinegar
6 tablespoons thinly sliced scallion greens
Cut the eggplants into batons about 3/4 inch (2cm) thick and 2 3/4 inches (7cm) long. Sprinkle with salt, mix well and set aside for at least 30 minutes.
Rinse the eggplant, drain well and pat dry with paper towels. Heat the deep-frying oil to around 390°F (200°C) (hot enough to sizzle vigorously around a test piece of eggplant). Add the eggplant, in two or three batches, and deep-fry for about 3 minutes, until tender and a little golden. Drain well on paper towels and set aside.
Carefully pour off all but 3 tablespoons oil from the wok and return to medium heat. Add the chile bean paste and stir-fry until the oil is red and fragrant: take care not to burn the paste (move the wok away from the burner if you think it might be overheating). Add the garlic and ginger and stir-fry until they smell delicious.
Tip in the stock or water, sugar and soy sauce. Bring to a boil, then add the eggplant, nudging the batons gently into the sauce so they do not break apart. Simmer for a minute or so to allow the eggplant to absorb the flavors.
Give the potato starch mixture a stir and add it gradually, in about three stages, adding just enough to thicken the sauce to a luxurious gravy (you probably won’t need it all). Tip in the vinegar and all but 1 tablespoon of the scallion greens, then stir for a few seconds to fuse the flavors.
Turn out onto a serving dish, scatter over the remaining scallion greens and serve.