Hiyashi Somen

To prepare the dashi, combine Water for dashi and Kombu in a saucepan. Let the Kombu soak for 30 minutes. Heat the saucepan over medium-low heat. Just before the Water for dashi comes to a boil, remove the Kombu.

Bring the Water for dashi to a boil, then turn off the heat. Add the Katsuobushi and let it steep for 5 minutes. Strain the dashi through a fine-mesh sieve, discarding the Katsuobushi.

To prepare the tsuyu dipping sauce, combine the prepared dashi, Usukuchi soy sauce, Mirin, Sake, and Granulated sugar in a clean saucepan. Bring the mixture to a gentle simmer over medium heat, stirring until the Granulated sugar is fully dissolved. Remove from heat and let the tsuyu cool completely, then chill in the refrigerator for at least 1 hour.