Sealed cooking is just the tonic
The theory and practice of maintaining health through diet has a long history in China, reaching as far back as the 6th century BC and the founder of Taoism, Lao Tzu. An expression that sums up this belief, that is thought to have been around for almost as long, says 'medicine and food are from the same source'.
Double-boiled soup, which has also been part of the Chinese diet for a considerable time, is a classic example of this. 'Double-boiled soup is closely linked to Chinese medicine and has developed as a way to replenish and nourish what our body is lacking and to build up vital energy,' says head chef Chan Lap Sun, of the Tsim Sha Tsui branch of Tsui Hang Village.
Assistant head chef at the IFC branch of Cuisine Cuisine, Tsang Pik-keung, attests to the power of double-boiled soup. 'I was asked to design a new soup menu for the restaurant, and had to do many soup tastings every day. After several weeks of tasting, I discovered that my face was glowing [with health] and my skin became softer and smoother than before. It is the most natural way for health and beauty.'
The soup is not boiled twice, as the name suggests. Instead, the ingredients are put in a ceramic vessel with a double-lid (ceramic is preferred but any sealable, heatproof container can also be used) and then partially submerged in a pot of simmering water. In a restaurant setting it is sometimes made by placing a soup pot over a simmering saucepan of water or by putting the ceramic vessel in a steamer. The soup cooks slowly from the heat of the water or steam. On average it is cooked for four hours, although it can be much longer with the exact cooking time depending on the ingredients and tradition.
'Take it slow to get the best results; quality is more important than quantity,' says Ngai Hong-kin, chef de cuisine at Sha Tin 18, quoting a popular expression.
'The Cantonese believe drinking soup is good for well-being, which is why having soup is a regular habit; for some, a daily habit,' says Tak Chan Yan, executive Chinese chef, at the Four Seasons Hong Kong. He says the double-boiling results in a 'healthy concentrated food extract'. The combination of ingredients used is often determined by the seasons. Chan says: 'People have different double-boiled soup in different seasons, so as to balance the inside of the body with the changing climate.' For example, to combat the cold of winter, soups with warming, nourishing qualities, such as chicken soup with wild ginger, are served.
Ngai explains that as the soup itself is not checked during the cooking time, there is no liquid evaporation, so in theory there is no loss of nutrients or flavour. This allows the soup to retain its essences (taste, healing properties, nutrient value, moisture), thereby providing the most benefit to the consumer.
In traditional Chinese medicine terms, double-boiled soup utilises the ingredient's chi, in other words it is an effective way to easily digest and absorb a lot of nutrients from a small amount of soup.
'We believe that the ingredients will slowly release their nutrients and flavours, which will be kept in the soup. Additionally, according to the concept of yin and yang, steam is moisturising and soothing, which is better for health,' says Ngai.
Chan adds: 'Among the three cooking methods of soup, slow cooking, simple boiling and double-boiling, double-boiling is the most effective method to capture the ingredients' nutrients.'
Tsang favours the technique when using high-end ingredients in soup such as fish maw, sea cucumber and bird's nest. These items defy the usual rule of not opening the soup pot while cooking as the delicate ingredients should only be added towards the end of the cooking time.
In addition to seasonal soups, there are double-boiled soups designed for specific or multiple ailments or for just looking good. For example a double-boiled soup of Sichuan lovage rhizome, tall gastrodia tuber and fish head is used to cure headaches and improve blood circulation. Chicken consomme with buffalo milk, a soup famous from Shunde, is said to moisturise the skin, build up muscle and boost blood circulation.
While it is not a complicated procedure to make double-boiled soup, it does take time and research to understand the nature of the ingredients (yin, yang, neutral and health properties) to create the most beneficial combinations, especially when using medicinal items.
The chefs agree that double-boiled soup has gone through little evolutionary change over the centuries, save for better quality ingredients and electric double-boilers.