Can I set up a stall to sell iced jiaozi and cook it in advance?

You can't. Stalls are not allowed to cook frozen jiaozi in advance. Cooking in advance will affect the taste of jiaozi, which is not as delicious as cooking now, leading to the loss of customers. Tangyuan, also known as "Tangtuan" and "Floating Zi Yuan", is one of the representatives of traditional snacks of Han nationality and the most distinctive food of traditional Lantern Festival in China.