METHOD

1. Rinse the beans and soak them overnight in 1 L of water. This soaking water is not included in the ingredient list.
2. Transfer the beans to a pot and add 2.5 L of clean water. Simmer gently until they crush easily between your fingers, about 3–4 hours.
3. While the beans cook, combine the kōji with filtered water and moisten evenly. Rest for 10 minutes, then work in the salt thoroughly with your hands.
4. Drain the cooked beans, but do not discard the cooking water. Let it cool; you may need some of it to adjust the texture later.
5. Mash the warm beans well with a potato masher or sanitized food processor until as soft as an earlobe. Add a little reserved cooking water only if needed.
6. Add the salted kōji mixture to the mashed beans and combine evenly.
7. Form the mixture into several firm balls, like snowballs.
8. Pack the balls into a ceramic container. Cover lightly with plastic wrap, press out as much air as possible, and weight the surface to seal it. Alternatively, use a large Ziplock bag and press out the air as you close it tightly.
9. Ferment for at least 6 months in a cool, dark place away from direct sun. Keep the temperature around 17 °C / 63 °F.