Fermented black beans are a common flavoring used in Asian dishes. They are made by salting and fermenting soybeans; the process turns the beans black. These beans should not be confused with common black beans, as they are completely different and not interchangeable. In China, these fermented black beans are known as douchi and are a common flavoring in a variety of Chinese dishes.
Fermented black beans are used in stir fries and fish dishes. Typically, the beans are used sparingly, as the salty, pungent taste can become overwhelming if overused. The taste is sweet and bitter, very sharp, and very salty. Due to these characteristics, fermented black beans are often combined with other strong spices or foods, such as garlic. Before being used in a dish, fermented black beans are sometimes rinsed so the flavor will not be overly salty.
Douchi is a common flavoring in Cantonese dishes like shrimp with lobster sauce. Douchi is available in some grocery stores, but in some areas, it is only available in Asian markets. Commercially made fermented black bean paste or sauce is more common in grocery stores and is contained in small glass jars, while actual fermented black beans typically come in a plastic package to preserve the flavor.
A common way to use douchi is to mash up the beans with garlic and/or ginger until it has the consistency of a paste. The paste can be spread on meats prior to cooking, or added to hot oil before adding the meat. Other ways to use douchi is to add it to vegetables as they are steaming. If using the black bean paste as a substitute, simply add the paste along with any other sauce ingredients toward the end of cooking a stir fry, meat, or fish.
The versatility of the fermented black beans is a draw for many cooks. Simple dishes can be accented with the beans, resulting in a more flavorful dish. For example, the black beans can be added to a simple stir fry of string beans, broccoli, or any other vegetables for a zestier flavor that is not overwhelming. Add chicken or pork to the mixture, stir fry for several minutes, then serve the dish over rice. Dishes like this usually have some sort of sauce in addition to the flavors of the black beans, as the douchi is meant to be an accent to the flavor, not the main flavor itself. Some cooks recommend crushing the black beans with a flat knife or a spoon before cooking to release the flavors.