Niku Soba

To prepare dashi: Place kombu and water in a pot. Heat gently over medium-low heat. Just before the water boils, remove the kombu. Bring the water to a boil, then turn off the heat and add katsuobushi. Let steep for 5 minutes, then strain the dashi through a fine-mesh sieve, discarding the katsuobushi.

To prepare the tsuyu (broth): In a separate pot, combine 600g of the prepared dashi with 40g koikuchi soy sauce, 30g mirin, and 20g sake. Bring to a gentle simmer and keep warm.

To prepare the thinly sliced beef: Heat a pan over medium heat. Add the thinly sliced beef and cook until browned. Drain any excess fat. Add 40g koikuchi soy sauce, 30g mirin, 20g sake, and sugar to the pan. Simmer until the liquid is slightly reduced and the thinly sliced beef is tender and well-coated.