Steps

1. Cut the myoga in half lengthways, and cut each half into fine slices (around 2mm). Soak them in water then drain. Slice up the spring onion and shiso leaves. Skin and grate the ginger.
2. Boil the somen noodles according to the pack instructions, then drain and rinsei under running water. Squeeze and turn until their stickiness is removed. Drain the noodles, and arrange in a bowl with some ice.
3. Serve the cold dashi soup in a deep pot. Arrange the myoga, ginger, shiso leaves and toasted sesame seeds on a small plate. These are then added to the cold dashi to taste, before dipping the noodles in.