Smoky Sea Stock

Tosa Dashi

The waters of Tosa Bay, off the Kōchi coast, teem with a tuna-like fish called katsuo, or bonito. In the early summer months the catch is served fresh, but year-round bonito is dry-roasted to make fish flakes called katsuo bushi. These fish flakes are used to make basic sea stock and to add a smoky flavor to a number of other sauces and stocks as well. This stock, named after the bay where bonito is caught, can be used in lieu of the basic sea stock in any recipe.


  • 1 quart dashi (basic sea stock)
  • 2 tablespoons soy sauce
  • 2 tablespoons mirin (syrupy rice wine)
  • 1 packet (5 grams) or loosely packed katsuo bushi (dried bonito flakes)


  1. Season the basic sea stock with the soy sauce and syrupy rice wine. Bring the mixture to a boil and simmer for 5 minutes.
  2. Remove the pot from the heat, and sprinkle the fish flakes over the surface of the seasoned stock. Let the broth stand for 2-3 minutes, until the flakes begin to sink.
  3. Strain the broth immediately through a cloth- or paper-lined colander.