I just made this soup after having forgotten it for a while (used to make it twice a month). It's simple and really good. It's based on a Japanese theme but I don't know if it actually is a soup they serve in Japan. I got the recipe from a friend in L.A. years ago. I've long ago lost the recipe but I hope this gives you an idea of how to do it.
1 small head of Napa cabbage - shredded
1 onion cut into smallish chunks
a handful of reconstituted or fresh shitake mushrooms sliced
some chicken meat - I use a combo of white and dark cut into chunks small enough to fit into a soup spoon.
The broth is 1/2 water and 1/2 chicken stock brought to a boil.
half of a small pkg of udon noodles or whatever you have on hand.
I cook the noodles separately (according to pkg directions).
Dump all the above ingreds into the broth and turn off the heat. You don't want the chicken to overcook and get tough.
Serve with the following sauce:
1 small daikon radish grated fine
1 large orange - grate the peel and then squeeze the juice.
Soy sauce - about 2/3 cup
Mix the radish, orange zest and juice into the soy sauce and serve on the side with the soup.