Tighten the mouth to avoid cracking during evaporation.

If there is no exhaust and the fillings are wrapped directly, those bubbles will form cavities during the steaming process. Therefore, whether it is some Chinese pastries or Western breads, after one fermentation, they must be vented, and then fermented for 10-15 minutes in the middle to allow the dough to relax, and then filled or shaped. Otherwise, once filled or shaped, it will no longer be possible to poke holes, which will cause the dough to collapse at the air holes.