1To prepare dashi stock, combine 400g of water with Kombu in a pot and let it soak for 30 minutes. Heat the pot over medium heat. Just before it boils, remove the Kombu. Add Katsuobushi to the simmering water, turn off the heat, and let it steep for 5 minutes. Strain the dashi stock through a fine-mesh sieve, discarding the Katsuobushi.