This is a very fast soup, especially if you use the instant dashi granules. You can add whatever seasonal vegetables you like, of course. Soba noodles are very thin Japanese noodles made from buckwheat. If you can’t find them, use any very thin noodle available.
Rinse the Dried mushrooms and then cover them with boiling water and allow to soak for 10 minutes. Drain, cut off and discard the stems, slice thinly, and set aside.
In a deep saucepan over medium heat, bring the dashi to a simmer, and add the mirin and soy sauce. Simmer for 3 or 4 minutes to evaporate the alcohol from the mirin.
In a separate saucepan, cook the noodles in boiling salted water until just tender, 3 to 4 minutes. Drain and rinse with cold water.
Add the mushrooms to the dashi mixture and simmer for 2 to 3 minutes. Add the carrots, celery, and tofu and simmer for a minute or two until the vegetables are crisp-tender. Divide the noodles and watercress among warm bowls and ladle the hot soup over them. Garnish with the green onions and serve.
© 2004 John Ash. All rights reserved.