After frying one flat side of yaki-gyōza, water is added before the pan is sealed.
This two-stage method first browns the underside in oil, creating the crisp base associated with yaki-gyōza. Water is then poured into the pan and the lid is quickly fitted. The trapped steam cooks the upper portions and softens the wrappers without sacrificing the browned bottom.
When most of the water has evaporated, the lid is removed so the remaining moisture can cook off. The dumplings may then be left briefly over the heat to re-crisp the base. Some recipes add starch to the water, producing a thin, lacy browned “skirt” around the dumplings.
Oil is used for the initial frying, but it is not the ingredient added to create the steaming stage. Stock or sake can appear in creative recipes, yet they are not the standard answer. Yaki-gyōza is one preparation among several: sui-gyōza are boiled, while age-gyōza are deep-fried.