How to Make It
Put the sweet potato noodles in a bowl, cover with cold water, and leave to soak for at least two hours. (You can soak them for half an hour in hot water, but they will be more likely to disintegrate during cooking.)
Cut the Chinese cabbage into 1 to 1½ inch ribbons, discarding any hard stalky bits. Put the pork in a bowl, and add ¼ teaspoon salt, 1 teaspoon of the Shaoxing wine, and the chopped ginger and spring onion. Mix well. Beat the eggs with the remaining Shaoxing wine, ¼ teaspoon salt, and 1 teaspoon cooking oil.
Pour 1 tablespoon of cooking oil into a frying pan and heat over a high flame until faint smoke starts coming off the sides of the pan. Pour any excess oil into a heatproof container, then add a little fresh, cool oil, and swirl it around the cooking surface. Over a gentle flame, put a 3-inch metal biscuit cutter in the pan, and pour about 1½ tablespoons beaten egg into the ring. When the egg is half set but still runny on top, put about 1 teaspoon of the pork mixture onto it, off center. Remove the ring with a potholder or chopsticks. Use a spatula to flip half the egg skin over the pork and press the edges down, to make a dumpling. (Some beaten egg may run out of the circle; if you are very fastidious you may trim this off!)
Remove the dumpling, which should be golden on both sides, and set aside; the pork does not need to be cooked through at this stage. Repeat with the rest of the egg and pork mixtures. You should end up with about 10 dumplings. (If you are not going to use them immediately, steam them over a high flame for 5 minutes to cook the pork through, then allow to cool and chill in the fridge.)
Drain the sweet potato noodles well, then put them in a heavy-bottomed pan with a lid that you can also use as a serving vessel. Put the sliced cabbage on top and add the stock, lard and soy sauces. Put the dumplings on the surface of the pot in an overlapping circle. Bring to the boil and season with salt and pepper. Cover and simmer over a medium flame for about 10 minutes, until the cabbage is silkily tender. Serve with a sprinkling of spring onion greens.
Salt pork, cabbage and egg dumpling soup. At the Old Jesse restaurant in Shanghai they serve this delicious soup: place a few slices of blanched Chinese ham or salt pork (unsmoked bacon, gammon, or pancetta work well) in a clay pot with plenty of sliced Chinese cabbage. Cover with stock, then crown with the egg dumplings. Bring to the boil, season with salt to taste and simmer for 8 to 10 minutes, until the cabbage is tender.