1 Cook the soba noodles in plenty of boiling, salted water for about 8 minutes. Drain, refresh in cold water and set aside.
2 For the broth, bring to the boil 1.2 l water, stir in the dashi and cook for 5 minutes. Add the bonito flakes and cook for a further 5 minutes. Strain the broth through a sieve and season with soy sauce and sake. Wash and sort the spinach and cook in a little boiling, salted water until it collapses. Then drain, refresh in cold water and drain thoroughly. Trim and wash the spring onions and cut into rings.
3 For the poached eggs, put 2 l water into another pan, bring to the boil and then turn down to a simmer. Add the salt and vinegar. Break each egg separately into a cup and carefully slide into the simmering water. Poach for 3-4 minutes.
4 To serve, put some noodles, spinach and 1 poached egg into each bowl and pour the boiling hot broth over. Scatter with spring onion rings and offer shichimi togarashi to season.