The rich broth called dashi may be the most important ingredient in the Japanese kitchen, used daily for soups. This version calls for iriko (dried baby sardines), which give the stock a surprisingly mellow flavor, but if you can't find them, add another ounce of dried bonito flakes. Steeping the ingredients overnight brings out the sardines' savory taste--when boiled, they get bitter.
1 1/2 ounces dried sardines (iriko)
2 dried shiitake mushrooms
3-in.-long piece kombu (dried edible kelp)
1 1/2 ounces dried bonito flakes (katsuobushi)
1/3 cup mirin
1/4 cup soy sauce
How to Make It
Break heads off sardines and remove the small black pellet of innards just beneath each head (they're dried, so this isn't messy). Put cleaned sardines, mushrooms, kombu, and 8 cups water into a medium pot. Cover and chill overnight.
Set pot over medium-low heat and bring to a simmer. When small bubbles form along sides and bottom of pot, but before it actually begins to simmer, remove sardines, mushrooms, and kombu.
Increase heat to high and bring to a boil. Add bonito flakes, pressing down with a spoon to submerge, and return to a boil; then immediately turn off heat. Let flakes settle to bottom of pot, about 15 minutes.
Strain broth through a cheesecloth-lined strainer into a bowl. Wring out all liquid from cheesecloth into bowl. Rinse pot, pour in strained broth, and heat over medium-high heat. Add mirin and soy sauce; simmer 5 minutes.