Bonito can be purchased at Asian or natural grocery markets.
plus 2 quarts more water for second batch
packed bonito flakes
Place optional kombu in saucepan with water.
Heat but do not let water boil.
As bubbles appear in hot water, but just before it simmers, remove optional kombu, setting it aside.
Add bonito flakes. Keep heat on under pot and allow water to come to boil. Then turn off heat immediately.
Bonito flakes will absorb water and slowly sink. Allow 3-5 minutes for this process.
Strain broth, reserving bonito. This is First Dashi.
For a second, stronger broth put 2 quarts more water back into pot with reserved kombu and bonito.
Heat water to barely a simmer (do not boil) for 10 minutes. Strain. This is Second Dashi.
*If you happen to be on the GAPS Introduction Diet, kombu is not allowed.