The reason why the ice-covered moon cakes sold in shops don't harden is that they use improvers, which make the flour not easy to age and keep the taste. At the same time, glutinous rice flour, rice flour and corn flour are used in making moon cakes with ice skin. If the proportion of these ingredients is appropriate, the ice skin can not be hardened easily. In addition, mooncakes with frosted skin need to be sealed to prevent them from hardening.