Just before the water starts boiling, add ⅔ oz katsuobushi (dried bonito flakes) and bring it to a boil again, skimming occasionally.
Once the water is boiling, reduce the heat, simmer for just 30 seconds, and turn off the heat.
Let the katsuobushi sink to the bottom, about 10 minutes.
Strain the dashi through a fine-mesh sieve over a bowl or measuring cup (reserve the spent katsuobushi and see below for what to do with it). Your Katsuo Dashi is ready to use.
To Store
If you are not using the dashi right away, store the dashi in a bottle or mason jar and keep in the refrigerator for 3–5 days or in the freezer for 2 weeks.
What to Do with Used Katsuobushi
Save the drained katsuobushi to make Homemade Furikake rice seasoning. If you don‘t use it right away, you can freeze it for 2–3 weeks.