Dou chi (豆豉), or "fermented black beans" in English, may not be Sichuan's most famous product, but these intensely flavored little nuggets nonetheless make an appearance in many of the region's most well-known dishes. As well as playing an important role in Sichuan's cuisine, dou chi are also widely used across China (particularly in the Cantonese tradition), and the Chinese-restaurant staple "black bean sauce" is served in Chinatowns from Los Angeles to Lagos.
Variations of dou chi abound across Asia, including Japanese natto, Korean cheonggukjang, and Himalayan kinema. But while these versions rely on added bacteria to speed up the fermentation process, Chinese dou chi usually have only salt added, making their fermenting time much longer, and their taste less overwhelming than that of their Japanese and Korean counterparts.
As well as being one of the most widely used of Chinese cooking ingredients, dou chi is also one of the oldest. Scholars believe they were used in cooking thousands of years ago, as far back as the Han Dynasty, making them one of the earliest known soy products in history. And not only are they tasty, but dou chi are also used by Traditional Chinese Medicine practitioners to relieve irritability, restlessness, and insomnia.
While referred to in English as "fermented black beans," dou chi is not made with the black turtle bean that is commonly used in the cuisine of the Americas and the Caribbean, but the soybean, which is soaked, steamed, and then fermented to produce a salty, pungent flavoring.
Although modern technology is often used to speed up the lengthy traditional processing method, a few old-school-style producers still dot the Sichuan countryside. One of these is the Southwest Flavorings Company, who make dou chi, fermented tofu and many other traditional Chinese cooking ingredients at their factory in Longquan, an hour from Chengdu.
At the Southwest Flavorings Company, the process from dried soy bean to finished product takes a whole year: First, the dried soybeans are soaked in water, and then steamed till soft. Next, any remaining liquid is squeezed out of them, and salt is added. Then the beans are packed into sealed containers and left to ferment for many months. At the Southwest Flavorings Company, the dou chi is available in 'original flavor', or with other ingredients are added, such as chili paste or sesame seeds.
Dou chi can be bought loose in open markets and is also available in small sealed packages from supermarkets. When buying dou chi, look for beans that are oily, plump and shiny, and remember to rinse them before use to remove any grit.
I like to add dou chi in small quantities to liven up simple stir-fries, and it's particularly good paired with fish. But it is perhaps most famously used in the much-loved Sichuan staple, Twice-cooked Pork, a recipe for which I've adapted from Fuchsia Dunlop's Sichuan Cookery and provided here.
300 to 400g half fat, half lean pork, in one piece
1 small piece of fresh ginger, sliced
8 suan miao, 'green garlics'
1 Tablespoon chilli bean paste (doubanjiang)
1 teaspoon sweet wheat paste (tianmianjiang)
1 Tablespoon dou chi
1 teaspoon dark soy sauce
1 teaspoon sugar
1. Bring a large pan of water to the boil. Add the ginger and the pork piece. Return to boil, and then simmer at a low heat for 20 to 30 minutes, until the pork is just cooked. Remove the pork, allow to cool, then place in a bowl with a little of the cooking liquid and refrigerate for a couple of hours (or overnight).
2. When the meat has cooled, slice it as thinly as possible, with each slice half fat and half lean.
3. Wash, top and tail the green garlic, and slice into 3cm-long chunks.
4. Heat the wok, and add about 2 tablespoon of cooking oil. Once hot, add the pork slices and stir-fry until they are slightly brown.
5. Now, push the pork to the side of the wok, and add the chili-bean paste to the space you made. Stir-fry for about 30 seconds, until the oil has turned red, then add the sweet wheat paste and dou chi and stir-fry for another few seconds. Now mix everything in the wok together, and add the soy sauce, sugar and salt to taste. You can add a little of the pork cooking liquid if it get too dry.
6. Finally, add the green garlics, mix and stir-fry until they are just cooked. Remove the finished dish to a serving plate, and eat with steamed rice.