Japanese
Make the dipping sauce (tsuyu) by combining dashi, soy sauce, and mirin in a small pan; bring to a brief boil, then cool.
Cook the soba in a large pot of boiling water for about 4-5 minutes until just tender.
Drain the noodles and rinse thoroughly under cold running water to remove excess starch and chill them.
Arrange the cold noodles on a bamboo mat or plate.
Divide the cooled dipping sauce into small cups and add spring onions and wasabi as condiments.
Garnish the noodles with nori strips and serve, dipping each mouthful into the sauce.