To make the dashi, gently wipe any sand that may be on the kombu with a damp cloth, but leave the white powdery substances as this contributes to the umami in the dashi.

Next, place the kombu into a large measuring cup or glass jug and then add the water. Let steep, in the refrigerator. overnight (approximately 10 hours). The kombu’s natural flavor comes out just from soaking it in the water.

Strain the dashi. It is now ready to be used. Store in the refrigerator for up to a week, or freeze for later use.

The kombu can be sliced and added to soups, stews, or salads.

*Note: To save time, you can also make the dashi using boiling water (nidashi). To do this, place the kombu and water into a pot and slowly heat over low heat for approximately 20 minutes. Skim the surface as needed. Just as the dashi comes to a simmer, remove the kombu and discard it. If you leave the kombu in, it will become slimy and potentially bitter tasting. Once done, strain and store as mentioned above — just be sure to cool the stock properly before storing.