1To prepare dashi stock: In a pot, combine 500g water and 10g kombu. Heat over medium-low heat until just before boiling, then remove the kombu. Bring the water to a boil, then turn off the heat and add 10g katsuobushi. Let katsuobushi steep for 30 seconds, then strain the dashi stock through a fine-mesh sieve, discarding the katsuobushi. Measure 400g of the prepared dashi stock.