When tiny small bubbles start to form at the bottom of the pan, turn the heat off and add all bonito flakes. *2
Wait for a few minutes or for the bonito flakes sink to the bottom of the saucepan.
Line a sieve with a sheet of kitchen paper towel and place it over a large bowl.
Strain the dashi into the large bowl.
Leave it till all the liquid has strained slowly. Do not squeeze out liquid out of the bonito flakes. *3
Use it for cooking or store in the fridge. *4
Notes
*1 Bonito flakes are featherly light. It looks like a lot but you need that much for 4cups/1 litre.*2 Do not boil the water. The water temperature should be around 185°F/85°C. If you add the bonito flakes into water at a hotter temperature, the dashi will lose its aroma and will become cloudy. It is best to be clear.*3 If you squeeze the liquid out of the bonito flakes, you extract an astringent taste of bonito as well. So be patient and strain the liquid naturally and slowly. *4 The Katsuo Dashi will last in the fridge for a couple days. If you are not going to use them in two days, keep the dashi in the freezer. It will last about 3 months frozen.