Remove the heads and dark parts of the guts from the niboshi. Break in half.
Gently wipe the kombu with kitchen paper. Add the water, niboshi and kombu in a pot. Leave overnight if possible.
Heat the pot over a medium heat, remove the kombu when it floats to the surface. After the water has come to a boil, simmer over low heat for about 5 minutes while scooping off the scum from the surface of the water.
Add 2 tablespoons of water (not listed), turn off the heat. Add the bonito flakes and turn the heat back on again. When it comes to a boil, turn off the heat.
After the bonito flakes sink to the bottom, pour the dashi stock through a sieve to strain.
Story Behind this Recipe
My mother used to make dashi stock with niboshi. I used a blend of niboshi, bonito flakes and kombu for my dashi stock. I sometimes add dried shiitake mushrooms.
When I'm in a hurry, I skip the step of soaking the ingredients. Scoop the scum off the surface frequently. This dashi stock is convenient and can be used for simmered dishes, soup or mentsuyu.