Preparations

Cut off the tips of the beans and cut longbeans into even lengths about 5 inches long. Rinse with cool water, then dry thoroughly to avoid spattering when fried.

Soak the shrimp in very hot tap water to cover until you can chew on one and enjoy its saltiness, about 15 minutes. Drain and pick through to discard any bits of shell.

Mince the ginger in the work bowl of a food processor fitted with the steel knife. Add shrimp and process with on-off turns until coarsely chopped. Add the preserved vegetable, process with 2 on-off turns to expose new surface, then scrape the mixture into a dish alongside the pork.

Alternatively, mince the ginger and coarsely chop the shrimp and preserved vegetable by hand.

The above may be done up to a day in advance of cooking. Seal the beans and condiments airtight and refrigerate. Bring to room temperature before cooking.

Deep-frying the beans

Divide the beans into 2 equal batches and put each on a flat plate. Have the beans, cooking chopsticks or a long wooden spoon, a large Chinese mesh spoon, a bowl to hold the fried beans, and a large lid all within easy reach of your stovetop.

Heat a wok or a large, very deep, heavy skillet over high heat until hot. Add the oil, leaving 3–4 inches free at the top of the pot to accommodate bubbling. Heat the oil to the dense-haze stage, 400° on a deep-fry thermometer, when a thick haze is visible above the surface but the oil has not yet begun to smoke. Adjust the heat so the temperature does not climb, then test the oil with a single bean. It should come immediately to the surface surrounded by white bubbles.

Return the heat to high and slide the first plate of beans into the oil. Shield yourself from spatters by holding the pot lid several inches above the oil and angled away from you. Do not cover the pot. Give the beans a gentle stir to even them. After about 30 seconds, the bubbling will die down and you can put the lid aside.

Fry the beans over high heat for about 4 minutes or until thoroughly wrinkled, stirring occasionally. Remove them from the oil with the mesh spoon, hold briefly above the pot to drain, then transfer to the empty bowl or pot. If fried properly, the beans will look limp and pitiful.

Wait a full 3–4 minutes or longer for the oil to regain a temperature of 400°. Test again with a single bean, then repeat the process with the next batch. When both batches are fried, tip the bowl to drain off excess oil. The beans may be left uncovered at room temperature for several hours before continuing.

Once the oil cools, strain and bottle it for future use.

Stir-frying the beans

Combine the sugar and salt with the stock, and leave the spoon in the bowl. Have the beans, the minced condiments, the combined liquids, and the remaining ingredients all within easy reach of your stovetop.

Heat a wok or large, heavy skillet over high heat until hot enough to evaporate a bead of water on contact. Add 2½ tablespoons of the deep-frying oil and swirl to coat the pan. When the oil is hot enough to sizzle a bit of ginger, add the minced mixture and pork. Stir-fry briskly, chopping and poking the pork to break it into tiny bits, adjusting the heat so it sizzles without scorching.

When the pork is 90 percent gray, give the liquids a stir and add them to the pan. Stir to blend, then raise the heat to bring the mixture to a simmer. Add the beans and toss to combine until most all the liquid has evaporated. Rapidly sprinkle in the vinegar, fold in the sesame oil and scallion, then turn off the heat.

Taste and adjust if needed with a bit more salt, sugar, or vinegar. The taste should be very zesty. When you have the taste you want, scrape the mixture into a large serving bowl or plate.

For best flavor, let the beans stand several hours at room temperature or refrigerate overnight once cool, stirring occasionally. Serve at room temperature, not cold, to enjoy the full flavor and aroma. Just before serving, garnish with a fresh sprinkling of scallion.

Leftovers keep beautifully, sealed airtight and refrigerated, for 3–4 days. Bring to room temperature before eating, stirring up the oils and seasonings from the bottom of the dish.