Douchi is whole soybeans (Glycine max) fermented with mould and salt until they turn soft, black, wrinkled and intensely savoury — the pungent umami base of Cantonese black-bean sauce and countless Sichuan and Hunan dishes. Unlike the smooth pastes and sauces made from them, douchi keeps the bean whole: each glossy, salty morsel bursts with a funky, winy, faintly bitter depth that seasons steamed fish, stir-fried greens and braises. Salted, dried and keeping almost forever, it is one of China's oldest and most influential foods — the ancestor of soy sauce, miso and doenjang alike.