Great on their own, Chinese jiǎozi get a fantastic flavor boost when dipped in a zippy sauce like this one. The tart-salty-spicy combination adds a complex edge to the dumplings.
There’s no such thing as a definitive dipping sauce, since cooks and diners mix up their own according to personal taste. At the least, your sauce should be tangy and savory. But add some nutty, hot chile oil, and your eating experience will enter a different orbit. Chinese dumplings are wonderful with an extra kick of ginger or garlic in the sauce, too. I prepare the sauce in advance, but you can set out the ingredients and invite guests to do it themselves.
Combine the soy sauce, vinegar, and sugar in a bowl. Stir to dissolve the sugar. Taste and adjust the flavors to your liking for a tart-savory balance. Add as much chile oil as you like for some heat. The sauce can be prepared several hours in advance up to this point. Right before serving, add the ginger or garlic for a fresh layer of punch.