Primary Dashi

Wipe the konbu, gently, with a damp cloth. Add water to a saucepan, with the konbu, and let stand, covered, 6–8 hours.

Remove lid and bring water to a near boil over low heat. (If you’re pressed for time, skip the soaking, but simmer the water and konbu gently at 149°, 1 hour.)

Remove konbu just before the water boils (it will give off a strong smell and bitter flavor if boiled at this point). Press the fleshiest part of the konbu with your finger. If konbu is soft, sufficient flavor has been obtained. If konbu is tough, return it to the pan for a few more minutes. (To keep the water from boiling add a little more cold water.)

Bring the stock to a boil, then immediately add bonito flakes; remove pan from heat; do not stir. Allow the flakes to settle to the bottom of the pan for a few minutes. Skim any foam from the surface and pass dashi through a strainer lined with cheesecloth; do not press. Dashi will keep in the refrigerator for a few days or in the freezer for 3 months.