Place the water and kombu in a medium soup pot, cover and bring to a boil. Remove the kombu after 5 minutes and set aside for future use or discard. Cut the daikon into half inch thick rounds and then quarters. Place the daikon and taro (albi) potato in the pot, cover and simmer for 5 minutes. Next, add the carrots, cover and simmer 1 to 2 minutes. Add the bonito flakes. Reduce the flame to low and add the dissolved miso, mix and simmer without boiling for 2 minutes. Add the spinach or watercress and simmer 1 minute.
When the soup is almost ready, pan-fry the mochi according to package directions, on both sides, until it puffs up. Place two pieces of mochi in each individual serving bowl. Ladle the soup into bowls and garnish with scallions before serving.
Per serving - 207 calories, 2 g fat (10% calories from fat), 6 g protein, 43 g carbohydrate, 6 g fiber, 0 mg cholesterol, 473 mg sodium