The koji mushroom has been used in Japan for centuries to ferment food. This method gives food a variety of flavours. Fermented foods such as miso and shoyu, which are made with koji, are gaining popularity due to their health benefits, cultural significance and sustainability. Sibylle Hunger offers step-by-step instructions for making your own koji ferments as well as tips for utilising leftovers. The recipe section includes traditional Japanese specialities and modern variations, prepared with local ingredients.