Wash the spring onions, cut into bite-sized pieces (approx. 2 - 3 cm) and mix with the whisked egg.
Put all the ingredients for the soup in a saucepan and simmer on medium heat. If necessary, wash the udon noodles, depending on the package insert, and add to the boiling soup until they are ready.
Fry the prepared egg mixture in a pan. Serve the noodle soup and the finished egg mixture and, if necessary, sprinkle with pepper (preferably Japanese pepper) or togarashi spice mixture.