Rice Kōji

Method

1. Wash 300 g of short-grain rice in several changes of cold water, rubbing gently, until the water runs almost clear. Cover generously with cold water and soak for 12 hours in a cool place, then drain in a colander for 1 hour so the surface dries a little.
2. Line a steamer basket with a clean cotton cloth, tip in the drained rice and fold the cloth over. Steam over vigorously boiling water for 45 minutes. The grains should be translucent and springy, soft outside with a firm core (gaijū-nainan) — never wet or porridgey. Sterilise your hands, the mixing bowl and the cloth with boiling water or spirit while it steams.
3. Turn the hot rice onto a clean cloth on a tray and spread it out, rubbing the lumps apart with your fingertips until the grains are separate. Let it cool to body temperature, 35C — hotter kills the spores, colder slows the start.
4. Tap 0.3 g of tane-kōji through a fine tea strainer over the rice in three passes, tossing and rubbing the grains between your palms after each pass so the spores coat everything evenly. Gather the rice into a mound, wrap it tightly in the cloth, set it in a covered wooden or plastic tray and hold it at 30C — a proofing box, a yoghurt maker or a warmed cool-box with a bottle of hot water all work.