Juwari Soba

To prepare the dashi, combine kombu and water (for dashi) in a pot. Heat gently over medium-low heat, just until small bubbles form around the kombu, then remove the kombu before the water boils. Bring the dashi water to a boil, turn off the heat, add katsuobushi, and let steep for 30 seconds. Strain the dashi through a fine-mesh sieve, discarding the katsuobushi.

For the tsuyu dipping sauce, combine the prepared dashi, koikuchi soy sauce, and mirin in a small saucepan. Bring to a gentle simmer, then remove from heat and let cool completely.

Place the buckwheat flour in a large mixing bowl. Gradually add water (for dough) to the buckwheat flour, mixing with your fingertips until coarse, shaggy crumbs form.