11. To prepare the dashi stock, place the Kombu in the Water in a medium pot and let it soak for 30 minutes. Heat the pot over medium-low heat. Just before the Water comes to a boil, remove the Kombu. Add the Katsuobushi to the Water, bring to a gentle simmer for 30 seconds, then turn off the heat. Let it sit for 5 minutes, then strain the dashi through a fine-mesh sieve, discarding the Katsuobushi.