In the Kamakura period (1192-1333), miso soups like this one, served with rice and pickled vegetables, became everyday fare in Japan.
- 1⁄4 oz. kombu (dried kelp)
- 1 cup bonito flakes
- 1⁄2 oz. wakame (dried seaweed)
- 2 Tbsp. akamiso
- 4 Tbsp. shiromiso
- 7 oz. firm tofu, drained, rinsed, and cut into 1/4'' cubes
- 2 scallions, trimmed and thinly sliced
Wipe kombu with a damp paper towel, then place in a container, add 4 cups water, cover, and refrigerate overnight. Remove and discard kombu.
Bring kombu stock to a boil in a medium pot over medium-high heat. Add bonito flakes, cook for 10 seconds, then remove pot from heat. Let stand for 2 minutes, then strain dashi (stock) through a sieve lined with cheesecloth. Discard bonito flakes. (If you're not using dashi immediately, it may be stored in a covered container in refrigerator for 1 week or in freezer for up to 1 month.)
Put wakame in a bowl, cover with cold water, and soak until soft, about 10 minutes. Rinse well to remove salt. Cut away any hard ribs, then slice wakame into 1'' pieces.
Pour dashi into a medium saucepan and bring just to a boil over medium-high heat. Whisk in akamiso and shiro-miso until they dissolve, then reduce heat to low. Do not allow soup to return to a boil. Add tofu and simmer for about 1 minute. Just before serving, divide wakame and scallions between 4 soup bowls, then fill each bowl with hot soup.