If fermentation is needed, yeast or soda can be used for fermentation. When the temperature is high, it will ferment for 3 or 4 hours, and when the temperature is low, the fermentation time will be longer, generally expanding to 2 or 3 times the original volume. Making steamed stuffed bun skin: after the dough is fermented, put it on the panel and knead it until there is no gas, then knead it into long strips, pull it by hand or cut it into pieces with a knife. The size is up to you. Then roll it with a rolling pin into a thick skin in the middle and thin skin on the side. If it's simple, you can just make it into a skin by hand. You can mix the stuffing in advance according to your own preference, and then wrap it in the bun skin. Put the skin stand on the center of the left hand, pinch a little edge with the thumb and forefinger of the right hand to form a fold, and then pinch it a little counterclockwise along the skin until it is sealed. You can pinch as many pleats as you want, and the smaller the pleats, the less the big pleats.