Seasoned Soy Concentrate (Shojin Tsuyu No Moto)

  • 75 sq cms (12 sq in) dried kelp (kombu)
  • 4 or 5 stems dried shiitake mushrooms, or 1 large dried shiitake mushroom
  • 80 to 120 ml (1/3 to ½ cup) Japanese soy sauce (shoyu)
  • 2½ to 3 tablespoons sugar
  • 1½ to 2 tablespoons sake
  • 1 tablespoon mirin (optional)
  1. Put the kombu, mushroom stems, and soy sauce in a small deep saucepan. Cover and let stand at room temperature for at least 1 hour or up to 12 hours.
  2. Add the sugar and sake to the pan and place over low heat. Cook, stirring occasionally, until the liquid begins simmering. Taste, and if very salty, add the mirin to mellow the flavour. 
  3. Adjust the heat to maintain a slow, steady simmer. Expect the sauce to foam.
  4. Simmer for 3 to 4 minutes, or until reduced by nearly half, and the sauce has become a bit syrupy. Remove from the heat and let the sauce cool naturally to room temperature.
  5. Pour the cooled concentrate into a small glass jar, leaving the kombu and mushroom stems behind. Cap the jar tightly and refrigerate for up to 1 month.