4 cups cold water
5 inch piece kombu (kelp, find in Asian market)
3 whole shiitake mushroom
pinch dried wakame (kelp, similar to kombu)
2 tablespoon sake
2 tablespoon mirin (sweet rice wine)
1/2 teaspoon sugar
2 1/2 tablespoon shoyu (Japanese soy sauce)
Dust off kombu and cut with scissors 3/4 of the way though.
In a pan, add water, kombu and shiitake and soak for about 1 hour.
Then, bring the pot nearly to the boil, and remove kombu, add wakame and bring to boil, simmer for 5 min.
Add remaining ingredients and simmer for 2 mins, drain out shiitake and wakame.
I found this makes a lot so I freeze into ice cubes to use for later (when I want to make miso soup or udon oshiru (udon noodle soup).
I find many dried "instant" dashi always contain fish or seafood. This is not "instant" but tastes just as good.