Place the kombu in a pot with the filtered water and let it soak for about 30 minutes. This helps to extract the umami flavor.

After soaking, slowly heat the water with the kombu over medium heat. Just before the water starts to boil (when small bubbles begin to form), remove the kombu. This usually takes about 5-10 minutes.

Remove the kombu pieces from the water and cut into bite sized pieces (kitchen shears work best). Set aside on a small plate.

Bring the kombu water to a boil. Add the bonito flakes (or optional dried shiitake mushrooms) to the pot and let it boil for 2 minutes.

Remove the pot from the heat and let the bonito flakes settle to the bottom for a minute. Then, strain the broth through a fine-mesh sieve or cheesecloth into another pot or bowl. Do not strain if using mushrooms. Discard the bonito flakes. Hint: cats LOVE them.

Let the broth cool for 5 minutes and then add the kombu pieces back to the broth if you will enjoy it on its own. Leave the kombu out if you will use the broth as a base for soups or sauces.

Enjoy your dashi immediately on its own or as a base for soups, sauces, or other dishes.

If you have leftovers, you can store it in the refrigerator for up to a week or freeze for longer term storage.