2Prepare dashi stock: Gently wipe the Kombu with a damp cloth (do not wash). Place the Kombu in a pot with 600g of the Water. Heat over medium-low heat. Just before the water boils, remove the Kombu. Bring the water to a boil, then turn off the heat and add the Katsuobushi. Let it steep for 30 seconds, then strain the dashi stock through a fine-mesh sieve, discarding the Katsuobushi.