Because Wangzai milk is not needed, because Wangzai itself is sweeter. Last time I cooked it, I used a bag made by Huishan Hard Generation, with 2 egg whites and 2 spoonfuls of sugar. Before steaming, I put plastic wrap on the mouth of the bowl so that there will be no unevenness. Also, don't touch the milk when it is boiling. Otherwise the milk skin will be destroyed. You won't be happy without nipples. When you separate the milk skin from the milk, the milk skin will stay at the bottom of the bowl. When the milk and egg white are put in, the milk skin will naturally float up.