Rice koji (Seikyo's Yasaka label fresh organic koji)
Salt (or shima maasu, Okinawan salt)
450 g (490 g if using shima maasu)
Ethanol (70% alcohol content)
Wash the soybeans, and soak in plenty of water overnight.
Drain off the soaking water, and boil the soybeans in fresh water. Cook them slowly over medium-low heat for about 5 hours. Be careful not to let them burn.
Bubbles will rise to the surface as they cook so skim them off. Add water to the pot to cover the beans if the water level drops too low.
When the soybeans are soft they are done. You should be able to crush one easily between the thumb and forefinger of your opposite hand (your left hand if you're right handed).
Reserve 2 handfuls of the salt in a separate container. Mix the rest of the salt with the koji while breaking up the clumps with your hands. (The koji in the background has been mixed with salt.)
Spray a bowl or other container with 70% ethanol. Add the slightly cooled soy beans and mash them up using a potato masher. If a few bits of soybean are still left, it's fine.
Spray both hands with 60% ethanol, then mix the salt-koji and the mashed soybeans together well.
Add some of the soybean cooking liquid until the mixture is soft and dough-like, with a texture similar to how your earlobe feels. Form it into baseball-sized balls (these are called miso balls), as if you were making onigiri rice balls.
Spray a plastic storage box with 70% ethanol, and wipe it dry with a clean paper towel. Cover the bottom with some of the salt that was reserved in Step 5. (Leave some salt to sprinkle on top of the miso.)
Push the miso balls into the bottom of the plastic box so that there are no gaps. I don't throw the balls in. (Translator's note: some miso instructions say to throw the miso balls into the container to eliminate air pockets.) Verify that there are no air pockets by observing the miso from the outside of the box.
When all the miso balls are packed in, sprinkle all the remaining salt on top.
Spray the surface of the miso with 70% ethanol, and cover with plastic wrap. Spray again with ethanol and add another layer of plastic wrap.
Wipe off any soy beans that are stuck to the sides of the container, spray with more ethanol and put the lid on. Wrap in newspaper.
Store in a cool dark place. Open it up in about 5 months to check on it. Mix it up from the bottom with a clean paddle.
It's ready to eat in 6 to 10 months.
Story Behind this Recipe
Salt has different levels of sodium chloride (NaCI) depending on the type, so re-calculate the amount to add accordingly. Shima maasu contains 92% sodium, so I use 490 g or so.
Use clean containers and utensils, and spray them as well as your hands with 70% ethanol. You can buy food grade ethanol at the pharmacy. Adjust the alcohol content with water, and put it in a spray bottle to use.