Double steaming

Double steaming, sometimes called double boiling, is a Chinese cooking technique to prepare delicate food such as bird's nest soup and shark fin soup. The food is covered with water and put in a covered ceramic jar and the jar is then steamed for several hours. This technique ensures there is no loss of liquid or moisture (its essences) from the food being cooked, hence it is often used with expensive ingredients like Chinese herbal medicines.

In Cantonese, double steaming is called dun (simplified Chinese: 炖; traditional Chinese: 燉; pinyin: dùn). The meaning of the Chinese character for dun in Cantonese is different from that in Mandarin, because dun means to simmer or stew in Mandarin. This technique is also common in Fujian, a neighbouring province of Guangdong (Canton).

In ancient China, the double steaming method was based on the Chinese philosophy of maintaining health through diet dates as far back as the 6th century BC, when the founder of Taoism, Lao Tzu, famously said, “medicine and food are from the same source”.It was mostly used on the emperor's meal during the fall and winter of the year, when most people are more easily getting sick. The significant difference between its and other meals is that it can cooked expensive food and Precious medicinal materials into one meal. It was served to the emperor for nourishment purpose and continuded in modern time.

This technique is said to achieve the maximum extraction of flavour with little compromise to the flavour or texture of the ingredients used. It is therefore the method of choice for coaxing forth the delicate flavour. Full flavour extraction can take up to 5 hours.