200 g (7 oz) dried soba (at least 50% buckwheat) or fresh soba
For the tsuyu: 250 ml (1 cup) water, 5 g (5 cm square) kombu, 10 g (a big handful) bonito flakes, 60 ml (1/4 cup) soy sauce, 60 ml (1/4 cup) mirin
To serve: 2 scallions finely sliced, wasabi, grated daikon (optional), a sheet of nori, cut in strips
How to make it
Tsuyu (15 min + cooling): Soak the kombu in the water 10 minutes, then heat until just before it boils and remove it. Add the bonito, simmer 1 minute, strain. Add the soy and mirin, bring to a boil, and chill.
Cook (5 min): Boil the soba in plenty of water, stirring at first, for the time on the pack, usually 4 to 5 minutes for dried. Add a splash of cold water if it foams up.
Chill (2 min): Drain into a colander and rinse under cold running water, rubbing the noodles between your hands to wash off the starch, then plunge in ice water. Drain well.
Serve: Pile on a bamboo tray or plate, scatter nori, and serve with cups of tsuyu, scallions and wasabi to stir in. Dip, then slurp.
Tips
Save the cooking water (soba-yu); pour it into the leftover sauce at the end and drink it.
Hot version: dilute the tsuyu with 3 parts hot dashi and pour over hot noodles.