11. Prepare the dashi stock: Place the Kombu in a pot with 1500g of Water and let it soak for 30 minutes. Heat over medium heat until just before boiling. Remove the Kombu. Bring the water to a boil, then turn off the heat and add the Katsuobushi. Let it steep for 5 minutes, then strain the dashi through a fine-mesh sieve, discarding the Katsuobushi.