Look for bonito at Asian food markets or in the ethnic section of the supermarket. It's a traditional ingredient in miso soup, but if you can't find it, it's okay to omit it--just be aware that you'll lose the seafood flavor in the broth.
6 cups boiling water
1/4 cup dried shaved bonito (dry fish flakes)
2 tablespoons yellow miso (soybean paste)
2 tablespoons red miso (soybean paste)
1/2 teaspoon low-sodium soy sauce
1/2 cup enoki mushrooms
4 ounces firm tofu, drained and cubed
How to Make It
Combine water and bonito; let stand 2 minutes. Strain the liquid through a fine sieve into a bowl; discard solids. Bring the liquid to a boil in a large saucepan. Add yellow and red miso and soy sauce; stir well with a whisk until smooth. Divide the enoki mushrooms and tofu evenly among 6 soup bowls, and ladle 1 cup soup into each bowl.
I found this soup to be a little boring. My bonito might have been part of the problem. I had my bonito flakes in the pantry for a while but they were individually packaged so I thought they were still ok but maybe they had lost some of their flavor. I substituted instant miso since that's all my grocery store had. I also added a few slices of shiitake mushrooms and I liked the extra texture. If I made this again I would add some green onions.