Note: Kombu and katsubushi can be found in any Japanese market or in the International section of most well-stocked supermarkets. For best results, use real kombu and katsuobushi. Alternatively, you can use powdered dashi mix. Follow instructions on package.
- 1 1/2 quarts water
- 1/2 ounce kombu (approximate 4- by 6-inch piece, see note)
- 1/2 ounce grated bonito flakes (about 3 cups, see note)
- 6 tablespoons white or red miso paste, or a mix
- 8 ounces firm silken tofu, cut into 1/2-inch cubes (optional)
- 1/2 ounce dried wakame seaweed (1/4 cup, optional)
- 4 ounces fresh mushrooms, sliced if necessary (such as honshimeji, namako, or shiitake, optional)
- A handful of small live cockles (optional)
- 4 whole scallions, thinly sliced (optional)
Combine water, kombu, and bonito flakes in a large saucepan and bring to a boil over high heat. Reduce to a bare simmer and cook for 5 minutes. Remove from heat, let cool for 5 minutes, then strain through a fine-mesh strainer. Discard solids.
Return broth to a medium saucepan and set over low heat to keep warm, but not boiling. Place a fine mesh strainer in the broth and add the miso paste to the strainer. Use the back of a spoon to press the paste through the strainer into the broth, Discard and large grains that don't pass through.
Add tofu, wakame, mushrooms, and cockles (if using), and allow to cook without boiling until ingredients are warm and wakame has re-hydrated, about five minutes. Garnish with scallions (if using) and serve immediately.