1To prepare dashi stock, soak kombu in 600g of water for 30 minutes. Gently heat the water with kombu until just before boiling, then remove the kombu. Add katsuobushi, bring to a gentle simmer for 30 seconds, then turn off the heat and let steep for 5 minutes. Strain the dashi stock through a fine-mesh sieve.
2Rinse Japanese short-grain rice thoroughly under cold water until the water runs clear. Drain well, then add water (360g) to the rice cooker with the rinsed Japanese short-grain rice. Cook according to the rice cooker instructions.