Clean the kelp with a well wrung out damp cloth briefly *2
Fill a container with the water and add kelp to steep (soak)
Let stand overnight, remove the kelp the next morning. *3
Steep & Simmer (Nidashi) method
Clean the kelp with a well wrung out damp cloth briefly.
Fill a saucepan with the water and add kelp to steep for 30 minutes up to 1 hour.
Put the saucepan over medium heat. When the small bubbles form, turn the heat off. *4
Remove the kelp and transfer the kombu dashi to storing jar. *3
*1 If you can choose, buy Hidaka kombu. You need about 3x5.5 inch (7.5cm x 14cm) *2 Do not wash under running water, as it may wash off umami on the surface.*3 Do not throw away the leftover Kombu kelp. Make Tsukudani (Japanese side dish, condiment). The recipe and instruction is in the above post. *4 Don't let the dashi broth boil, as it loses the delicate flavour and aroma.