Can I use unpasteurized store bought miso to make more miso? I have some leftover chickpeas and red beans that I was thinking of making into a miso paste, but I don't have any koji and don't want to go searching multiple stores in the middle of a pandemic. Can I use store bought miso as the starter for making more miso? It says unpasteurized so I imagine that it is just dormant and can become active again. Has anyone done this before?
Maintaining a Koji culture is considered difficult, even commercial operations rarely do this. Meredith Leigh talks about it https://www.youtube.com/watch?v=4X-96_FFLyI&amp;t=11m35s
I think I may have read somewhere that the new Koji Alchemy book has good info on culture maintenance.
Most of my books on Koji don't even mention culture maintenance, although The Art of Fermentation by Sandor Katz does. It seems to be important to make sure there are plenty of nutrients. In Japan they add ash for this.

"When rice has cooled to body temperature, before inoculating, mix in sifted hardwood ashes, about 1.5 percent by weight of the quantity of dry rice you cooked. The ash provides potassium, magnesium, and other trace elements that promote healthy mold growth and sporulation."

Don't use white rice and do cook your substrate until it's quite soft.

Good luck!