Zaru Udon

Prepare dashi: Wipe kombu with a damp cloth. Place kombu and 600 grams water in a pot. Heat gently over medium-low heat. Just before the water boils, remove the kombu.

Bring the water to a rolling boil, then add 15 grams katsuobushi. Immediately turn off the heat and let it steep for 30 seconds. Strain the dashi through a fine-mesh sieve, discarding the katsuobushi.

Prepare tsuyu: In a small saucepan, combine the prepared dashi, 60 grams koikuchi soy sauce, 40 grams mirin, and 20 grams sake. Bring to a gentle simmer for 1 minute, then remove from heat. Let the tsuyu cool completely, then chill thoroughly in the refrigerator.