So, usually koji is made using soybeans, rice or barley, and then the koji, inoculated with spores also called koji, is mixed with (more) soybeans, chickpeas or some other legume to make miso, or used to make something else like amazake or some types of vegetable ferments.
But the Momofuku cookbook gives a brief mention to popcorn miso, made of unpopped kernels, and tasting of popcorn. It also mentions pistachio miso. So there are a lot of possibilities when you’re making your own koji, and I am determined to try some of them, despite my relatively poor history of being able to make miso. I have made sweet (i.e. 3 month) miso before, and just began a barley koji sweet miso a week or two ago. That’s manageable. But I really want to try 1-3+ year salty misos, and so far I have always managed to freeze or bake these while moving or living off-grid or whatever. But hope springs eternal, so I am trying again, using spores intended for red rice sendai (6-12 month) miso. At least by making my own koji, just buying spores instead of the inoculated rice, I end up with a lot more koji for a lot less cost.
So anyway, above are pictures of the koji in process. To make the koji you need to steam the popcorn (pre-soaked for 24 hours) until soft. I used bamboo steamers lined with cheesecloth, and had to do the steaming in two batches. Then when it had cooled down a little, I sprinkled the spores mixed with flour onto the koji, wrapped it all up in towels to insulate it, and stuck a thermometre in so I could monitor the temperature. So far both the barley and the popcorn koji have been good at keeping within the right temperature range without me having to do much. After 24 hours, I moved it to a pan and made furrows in the pan. After a day of inoculating, it gives off more heat, so while it still needs to be incubated a bit, it also would be easy to overdo it, hence spreading it out more and adding furrows. You can see in the second picture in the tray how much more white mold there was in the morning, compared to the night before, so it’s growing well.
Lately I have been branching out in how I use miso too. Travis introduced me to miso in savoury oatmeal, which I love for breakfast (sometimes with seaweed). I have also started adding sweet shiro miso to the one-ingredient frozen banana “ice cream” (that I always seem to bring up) for a salty-caramel-y flavour.