Soak the soy beans overnight (in 2-3 times as much water as the beans).
Boil the beans (until they can be mashed between your fingers). Since it's a small quantity, I boiled them for 15 minutes in a pressure cooker, then transferred to a thermos and let them sit for 2 hours.
While the beans are boiling, combine the koji with the salt (blend until the koji sticks together when squeezed).
Put the soy beans in a thick plastic bag, then mash them by stepping on them (or use a masher or food processor).
Combine the soy beans with the rice koji and salt from Step 3.
Transfer to a Ziploc bag. Press out the air as much as possible.
Put it into another Ziploc bag and let it mature in an upright position.
Story Behind this Recipe
For my son's school research project.
The photos show how it looks in a resealable storage container. Double bag it!! If you're still unsure, wrap it again in a plastic shopping bag.