Cheonggukjang is a fast-fermented Korean whole-soybean paste — a close cousin of Japanese natto — made by holding boiled soybeans warm with Bacillus for just a few days until they turn soft, sticky and stringy, then mashing them coarsely with a little salt, garlic and chilli. Pungent, ammoniacal and deeply savoury, it is prized less as a keeping paste than as the funky heart of cheonggukjang-jjigae, a quick, rustic stew simmered with tofu and vegetables. Where doenjang takes months to age, cheonggukjang is ready in days, and its sharp, penetrating aroma makes it one of the most divisive foods on the Korean table.