Put the konbu and water in a pot and turn on the heat. If you're going to eat this in the evening, you can just put the konbu in and let it soak all day to make a stronger broth. When it starts to boil, take out the konbu.
Cut the chicken into thin pieces. Remove the silvery membrane from the chicken gizzards and score the surface.
Julienne the napa cabbage (cut the leafy portion in half lengthwise first, and then cut across into thin strips). Thinly slice the onion against the grain.
Put the seasoning ingredients marked ● into a container and microwave for about 1.5 minutes. Add ginger and stir. If you are worried about the alcohol content, you can add the sake directly into the pot and boil it off that way.
Add the gizzards, salt, Aji-no-moto seasoning, and grated ginger to the pot and simmer a little. Skim off any impurities that float to the surface of the broth. Next, add the chicken thigh meat, then the onion, then the napa cabbage.
Once the napa cabbage has shrunk, add the tofu and mushrooms and simmer a little more.
Serve into individual dishes, and season to your taste with the ginger and soy sauce mixture from Step 4.
Story Behind this Recipe
My mother-in-law taught me this recipe that she has been using for years.
The amount of water should fill the pot roughly 70 percent. You don't flavor the contents in the cooking pot itself, so the amount of water used is flexible. The gizzards are optional; use or omit as you like. For those who really like napa cabbage, you can add more. I suggest cutting up a bunch and then adding more to the pot as you eat.