Add boiling water and salt to a rice cooker, and cool to 60℃. Add the koji while breaking it up, and mix.
Turn on the warming function, cover with a cloth, and let warm for 5 to 6 hours. Stir the mixture every hour.
Once the koji has softened, cool in room temperature. Place in a container that has been sterilized by boiling, and store in the refrigerator.
Some rice cookers don't allow for warming while the lid is still open. Please be sure to check beforehand.
Story Behind this Recipe
I was searching how to make shio-koji quickly when I I found a method where you can prep in the rice cooker. It's pretty much the same as making amazake. Rice Cooker Amazake - Recipe ID: 1745021 Reduced Salt Version - Recipe ID: 1745052
* You can use this immediately, but if possible let it age for 2 to 3 days at room temperature. * Adjust the amount of salt as desired.