Hegi Soba

Prepare dashi stock: Place kombu in 800g of water and let it soak for 30 minutes. Heat the water slowly over medium-low heat. Just before it boils, remove the kombu. Bring the water to a boil, then turn off the heat and add katsuobushi. Let it steep for 30 seconds, then strain through a fine-mesh sieve, discarding the katsuobushi. Set aside 400g of this dashi for the tsuyu.

Prepare tsuyu (dipping sauce): In a saucepan, combine 400g of the prepared dashi, koikuchi soy sauce, mirin, sake, and sugar. Bring to a gentle simmer over medium heat, stirring until the sugar is dissolved. Remove from heat and let it cool completely. Chill the tsuyu in the refrigerator until ready to serve.

Prepare funori: Rinse the dried funori seaweed thoroughly under cold running water to remove any sand or impurities. Soak the funori in 50g of water for 15 minutes until softened. Transfer the softened funori and its soaking water to a blender and blend until a smooth, thick green paste is formed.