This recipe uses kelp but no bonito flakes. Dashi is a basic soup stock. This recipe can be prepared in advance and stored in the fridge 2-3 days or frozen. Taken from Japanese Cuisine for Everyone by Yukiko Moriyama.
To clean the kombu, wipe it with a damp cloth. If you wsh it, some of the flavor will go away. Since bonito is not being added to this recipe, you want the full flavor of the kombu.
Soak kombu in the water for 1 hour.
After the 1 hour soak, bring water to a boil, removing the kombu just before the water starts boiling.