You'll often find these spicy wonton on dim sum menus, or in the dumpling section of Sichuan and Shanghainese restaurants. I like them as a light main course, served with boiled noodles and blanched or stir-fried green vegetables.
You'll need about 50-75 square wrappers for this recipe, depending on how generously you fill them. If you don't want to serve all the wonton at once, put them, uncooked, on a foil-lined metal tray and freeze until solid. Then take them from the tray and put into air-tight containers (or zip-lock bags) and freeze until needed. They can be boiled from their frozen state, adding about two minutes of cooking time.
The instructions on how to wrap wonton sound elaborate, but it's actually easy. If you have another method for wrapping wonton, by all means do it your way.
Put the minced pork in a bowl. Use a very sharp knife to cut the shrimp meat into small pieces. Finely mince the ginger and chop the spring onions. If not using chicken stock, put several ice cubes in a bowl and add 60ml (¼ cup) cold water.
Use your hand or long chopsticks to thoroughly mix together the pork, shrimp, soy sauce, rice wine, sugar, salt, white pepper, cornstarch, ginger and spring onions. Drizzle in about the cold chicken stock (or 45ml/3tbsp of iced water) and mix well (the cold liquid makes the dumplings juicier). Refrigerate for about an hour.
While the filling is chilling, make the sauce. Toast the Sichuan peppercorns in a small, unoiled skillet placed over a medium-low flame. Shake the pan almost constantly until the peppercorns are lightly toasted. Cool to room temperature, then pick and and discard the black seeds. Crush the peppercorn husks to a coarse powder in a mortar and pestle.
Stir the sugar with the vinegar until the sugar is dissolved, then mix in the soy sauce, chilli oil and sesame oil. Cut the chillies into small rounds, squeezing out and discarding the seeds as you go. Mince the garlic and onions and add them to the sauce mixture along with the chillies, toasted sesame seeds and Sichuan peppercorn powder. Taste the sauce and correct the seasonings, if necessary. It should taste spicy but balanced; if it's too hot, add a little more sugar.
Stack the wonton wrappers on a small plate and cover them with a folded up clean kitchen cloth. Pour some water into a small dish. Take one wonton wrapper from the stack (cover the others again with the cloth) and put it on your non-dominant hand with one corner (call it the "south corner") nearest you. Put a heaped teaspoonful of the filling on the wrapper, near the south corner. Fold up the edge of the south corner over the filling, then fold it again, so the meat mixture is completely wrapped, and about 1.5cm (⅔in) away from the opposite corner. Press on the wrapper at the sides of the filling, to seal in the meat and expel any air. Bring the east and west corners towards each other, dampen one of the edges and press the other edge over it so they overlap. Press firmly so the edges adhere. Place the filled wonton on a foil-lined tray. Continue with the remaining wrappers and filling, placing the wonton on the tray so they are not touching each other. If you're not cooking the wonton immediately, cover them with cling-film so they don't try out, then refrigerate.
When ready to eat, bring a large pot of water to the boil. Add the wonton, but do not crowd the pot - cook them in batches. The wonton will sink to the bottom of the pot, then will rise to the surface as they cook. When all the wonton are on the surface, start timing. Boil them for about three minutes, depending on how much filling they contain. Use a large slotted skimmer to scoop the wonton from the pot. Shake off as much water as possible, then put the wonton into individual bowls. Before cooking the next batch, skim off the foam from the surface of the water.
Serve the wonton with the sauce, letting each diner add as much as they want.