Gochujang
Korean chili paste made from glutinous rice, fermented soybeans, chili powder and salt, thick, hot, salty and faintly sweet.
Gochujang is a fermented paste made from glutinous rice or other grain, fermented soybean powder, Korean chili powder and salt, often sweetened with rice syrup or malt. It is deep red, dense and sticky, and its heat is rounded rather than sharp, carried by umami and a gentle sweetness that comes from fermentation. Because it is so thick, it is usually loosened with liquid, vinegar or oil before going into sauces, marinades or stews. Heat levels vary by type and are often indicated in grades on Korean packaging. It is sold in Asian grocery shops, in the Asian section of larger supermarkets and by mail order. Once opened, it keeps for many months in the fridge.
Substitute:
There is no real substitute, because the fermented depth and the sticky sweetness together carry the dish. As a stopgap, light miso paste stirred with Korean chili powder or other mild chili flakes and a little honey or sugar roughly matches the salt, heat and sweetness, but tastes flatter and less rounded. Chili sauces such as sriracha are too thin and too sour and change the dish noticeably.