关火前盖子开小缝，还是关火后？要不塌不皱的馒头真的好难 如何判断发酵好了没？蒸好后什么时候才可以开盖？

關鍵1 對的配方
材料
中筋麵粉 300g
糖 15g
酵母 3g
鹽 4g
牛奶 160g
油 1大匙 （約15cc，麵團成團後再加入）
關鍵2
麵團是否發酵好的三個判斷重點
關鍵3
冷水上鍋開大火。水滾後馬上開小縫蒸15分鐘
關火後，等5～10分鐘再開蓋
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Key 1 pair of formula
ingredients
All-purpose flour 300g
Sugar 15g
Yeast 3g
Salt 4g
160g milk
1 tbsp oil (about 15cc, add it after the dough becomes a dough)
Key 2
Three key points for judging whether the dough is well fermented
Key 3
Bring a hot pot on cold water. Steam in small slits for 15 minutes immediately after the water has boiled
After turning off the heat, wait 5-10 minutes before opening the lid