Tororo Bukkake Udon

Wipe kombu with a damp cloth. Place kombu and 1000 grams water in a pot. Heat gently over medium-low heat. Just before the water boils, remove kombu.

Bring the water to a full boil, then turn off heat. Add 20 grams katsuobushi, let it sink to the bottom for about 30 seconds. Strain the dashi through a fine-mesh sieve lined with cheesecloth, pressing lightly to extract liquid. Discard kombu and katsuobushi.

In a small saucepan, combine 400 grams of the prepared dashi stock, usukuchi soy sauce, mirin, and sake. Bring to a gentle simmer over medium heat, then immediately remove from heat. Let the sauce cool completely, then chill in the refrigerator.