Cook pasta as package directs, rinse and set aside. If using whole shiitake mushrooms, remove the stems, discard and slice the cap. Prepare the broth by placing the kombu, shiitake, shiitake soaking water and water in a pot. Cover and bring to a boil. Reduce the flame to medium low and simmer 5 minutes. Remove kombu (keep and use in other dishes), cover and simmer another 5 minutes. Reduce the flame to low and add the shoyu and mirin. Simmer 3 to 5 minutes. Place cooked noodles in bowls. Pour hot broth over. Garnish each bowl with equal amounts of bonito flakes, nori and green onions.
Per serving - 191 calories, 1 g fat (7% calories from fat), 8 g protein, 37 g carbohydrate, 4 g fiber, 0 mg cholesterol, 468 mg sodium