Koji, sometimes spelt kouji is a kind of yeast or mould called Aspergillus oryzae. Koji is also used to make many thing from Sake, to Soy Sauce, Amazake to Miso. Try marinating meat of fish in shio koji. Top a piece of steak with Shoyu Koji or make your own koji using Kome Koji dried inoculated rice grains. Unlock umami with koji, the backbone of Japanese flavour.