To make dipping sauce - place mirin in a saucepan and bring to the boil. Add dashi and soy sauce. When it boils for the second time, remove from heat, and let stand to cool. When cool, transfer to a bowl and chill in the fridge.
Boil a generous amount of hot water and cook fresh soba noodles. When done, rinse in cold running water, squeezing and turning the noodles with one hand to get rid of stickiness. Drain in a sieve.
Arrange the noodles on a serving platter with flaked nori pieces on top. Serve with dipping sauce and other condiments.