Kombu Dashi

Cold-brew method: Using scissors, cut the kombu, if necessary, so that it fits in your bowl or container (large enough to hold the water). Add the shiitake, if using. Cover with water and let stand at room temperature for 8 hours or overnight. Remove the kelp and reserve for use in other recipes. Remove the shiitake mushroom, squeezing out any excess liquid; you can use the rehydrated shiitake as you would fresh shiitake (just cut off and discard the tough stem). Pour the dashi through a fine-mesh sieve to strain.

Stovetop method: Using scissors, cut the kombu, if necessary, to fit in a heavy-bottom pot. Put the kombu and shiitake mushroom, if using, in the pot and pour in the cold water. Turn the heat on low. You want to gently simmer (not boil) it so that you have a clear broth. Let it simmer at a low temperature (about 150˚F/65°C) for 45 minutes to 1 hour. If using shiitake, remove it after 15 minutes; you can use the rehydrated shiitake as you would a fresh one (just cut off and discard the tough stem). Remove the kelp and reserve for use in other recipes. Strain the dashi through a fine-mesh sieve.

Use the dashi immediately or store it, covered, in the refrigerator for up to 3 days. Add it to miso soup, or hot pot, or use as you would vegetable broth.