Black bean sauce is a pungent, intensely savoury Cantonese condiment built on douchi — fermented, salted black soybeans — mashed or left whole and bound with garlic, oil and often a little sugar, soy and starch. Deeply funky, salty and umami-rich with a winey, almost wine-cellar depth, it is the backbone of stir-fries such as beef in black bean sauce, clams in black bean sauce and steamed spare ribs.