Marinating foods in shio koji makes them easier to digest while simultaneously bringing out the rich umami flavors of the dish.
Slice all mushrooms into bite-size pieces. Boil water and cook mushrooms in a pot for 2-3 minutes.
Drain water and mix with Shio Koji while mushrooms are hot. Transfer to air-tight container and keep refrigerated to marinate for as long as you prefer.
Once your are ready to use your koji-marinated mushrooms, add them to your broth of choice. You can also add Udon or Soba noodles as a topping or mix with steamed vegetables, if desired.