Ensure that all your equipment is very clean. Running it through a dishwasher is the easiest way to ensure cleanliness, but jars could also be placed in an oven at 90’C for 20 minutes, if a dishwasher is unavailable
Cool the cooked green lentils to room temperature
In a large bowl, mix the koji, lentils and salt
Massage them together for a minute or two, so the lentils release some liquid
Squash the mixture into a jar, trying not to leave any pockets of air
Wipe any stray miso from the walls of the jar
Sprinkle a fine layer of salt on the surface, to prevent mold from forming
Cut a piece of greaseproof paper or cling film to fit over the surface and then weigh down with a glass weight (a small jar filled with water that fits inside your big jar is perfect!)
Cover with a t-towel, to prevent flies from entering
Leave to ferment at room temperature for 6 months