What's a jiaozi?
Jiaozi are northern chinese style dumplings featuring a minced meat/poulty/seafood and/or vegatable enclosed with a chewy wheat flour dough and sealed by crimping. Beyond these simple ground rules, we face endless permutations of shape, cooking method, filling, dough type. In my mind, jiaozi are best classified according to their cooking method. After all, one of the most incredible features of jiaozi are the versatility of the components. Most fillings and doughs can be used for any cooking methods. There are some exceptions though. For example, really juicy fillings don't work as well with the pot sticker method because their water balloon nature is just too delicate. Or you may find that a particular filling or dough works better with a particular cooking method flavor and texture wise.
Shuijiao aka Boiling: Literally meaning 'water dumpling.' The traditional method is the 'three cups' method. Bring the water to a boil, add dumplings. When the water reaches a boil, add a cup of cold water, then bring to a boil again. Repeat two more times, and the dumplings are done. Personally, I've tried this technique and it's not a good one for timing doneness as there are too many variables to account for. It seems that this method was one of the few ways they had to quickly regulate the heat back when biomass or coal stoves were the only game in town. That said, occasionally you may want to turn down the heat to prevent foam overs or damaging turbulence. Better ways to check for doneness are the.feel of the dumpling, internal temp, or cut open a test dumpling.
Zhengjiao aka Steaming: Literally 'steam dumpling.' Good for delicate dumplings or for when you have inadvertently made your dough too wet or soft, as the dumplings will absorb the least amount of moisture in this method. I use a 30cm two tier stainless steel steamer I picked up on sale. Most rice cookers also come with a steamer basket. Bamboo steamers are pleasing to the eye, but you either need to use a wok (and destroy the patina you've worked so hard for) or need some sort of adapter to your pot. Many cooks I know keep two woks and use Barbara Tropp's system. One is only used for stir frying and thus it's non stick patina is protected. The other is used for steaming, deep frying, and tea smoking (methods that are destructive on and don't require the patina). The keys to good steaming are; make sure there are good gouts of steam coming from the top tier (don't stack them too high), line the steamer with cabbage/lettuce leaves or perforated wax or parchment paper to prevent sticking, rotate the tiers in the stack at least once to ensure even cooking. Check for doneness same was with boiled dumplings.
Guotie aka Potsticker Method: Literally means 'pan stick.' This method was invented by accident when a careless palace cook left his boiling dumplings on the stove for too long and 'burnt' the bottoms after the water evaporated. Luckily for us and the cook, his master loved the new style dumplings. Method is as follows: pan on fire, add a little oil to pan, arrange dumplings in pan, add some water, cover, cook until water is gone, uncover and turn heat down a little, crisp up bottoms, plate and serve. When adding water, remember that the intent is to steam, not boil. Use either a carbon steel pan or wok with a well developed patina, teflon pan or wok, or well seasoned cast iron. Crisping up for a longer period of time over a medium heat gives a better crust then a short time over a raging inferno. Choose a pan that will let you slide a spatula under the dumplings easily. I like to make a big pan of potstickers that are stuck together and can be inverted onto a plate all in one piece in a nice spiral design.
Age-gyoza aka Deep Frying: Literally deep fried dumpling (in Japanese). A method popular in japan. I have not used this with jiaozi type dumplings.
Jiaozi versus Wontons:
While they may superficially seem the same, they are two different animals. Wontons use a much thinner and delicate egg and wheat flour dough, and are usually boiled and served in soups, or occasionally deep fired. Wontons are associated with southern China, esp Cantonese style food. Jiaozi are more rustic in comparison, with their thicker, chewier skins.