Rinse and soak the soy beans in plenty of water the day before.
Boil until the beans become tender enough to mash between your fingers. This should take 4-5 hours, boil while skimming off the scum.
Leaving aside a bit of salt, thoroughly combine the rice koji and salt.
Drain the soy beans, and reserve the boiled liquid. Mash the soy beans, then thoroughly mix with the koji and salt mixture from Step 3, then add the reserved liquid until the mixture reaches the firmness of your earlobe.
Form the mixture into balls to press out any air, then pack into a sterilized bucket.
Liberally sprinkle the remaining salt evenly on top.
Cover with plastic wrap to prevent any air from entering, cover with a lid, then store in a cool, dark place.
Check the progress after 2-3 months, disard any mold that may have grown, then stir it up from the bottom. You should be able to start using it from the fall.
Story Behind this Recipe
Miso seems very difficult to make, but in fact, it's super easy! It's natural for mold to grow...
2 kg each of soy beans and koji will yield about 8 kg miso.