Hiyashi Tanuki Udon

Prepare the dashi: Combine 1000 grams of Water and 10 grams of Kombu in a pot. Heat slowly over medium-low heat until just before boiling. Remove the Kombu.

Bring the Water to a boil, then turn off the heat and add 20 grams of Katsuobushi. Let it steep for 5 minutes. Strain the dashi through a fine-mesh sieve, discarding the Katsuobushi.

Prepare the tsuyu: In a saucepan, combine 600 grams of the prepared dashi, 80 grams of Koikuchi soy sauce, 60 grams of Mirin, and 10 grams of Sugar. Bring to a gentle simmer, then turn off the heat and let it cool completely. Chill the tsuyu in the refrigerator.