11. Prepare the dashi stock: Place Kombu in 1500g Water and let it soak for 30 minutes. Heat over medium-low heat. Just before it boils, remove the Kombu. Add Katsuobushi, bring to a boil, then immediately turn off the heat. Let it sit for 5 minutes, then strain the dashi through a fine-mesh sieve, discarding the Katsuobushi.