This salty and chilli-flavoured fermented soybean paste is widely available in Luang Namtha markets. To create it, soybeans are steamed and then put in a plastic bag in the sun where they are left for a time. They are then pounded with dried chillies, rice alcohol and salt. The mixture is left for between a month and a year. The paste is used to make the sauce for kao soi noodles. Koreans make similar pastes called doenjang and gochujang. The closest equivalent is Chinese douban jiang, a spicy, salty paste made from fermented broad beans, soybeans, red chilli peppers, salt and spices native to Sichuan.
An easy substitute is to buy bottled fermented yellow bean sauce with whole beans, drain the liquid and mash 1 cup of the beans with 1 teaspoon chilli powder or 1 tablespoon chilli flakes. Miso, spiced up with chilli powder, can also be used.