Ingredients:

  Amount  Measure       Ingredient -- Preparation Method
--------  ------------  --------------------------------
     1/4  ounce         kombu -- dried kelp
   1      cup           bonito flakes
     1/2  ounce         wakame seaweed -- dried seaweed
   2      tablespoons   akamiso
   4      tablespoons   shiromiso
   7      ounces        tofu -- firm, drained, 1/2"
                        -- cubes
   2                    scallions -- thinly sliced

Preparation:

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 are 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 in a medium saucepan and bring just to a boil over medium-hig heat. Whisk in akamiso and shiromiso 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.