Cut the kamaboko into approx. 5mm wide slices. Remove the roots of the spring onions and cut the spring onions diagonally into thin pieces.
Put the dashi in a saucepan and bring to the boil over medium heat. Add mirin and soy sauce. Salt, bring to the boil again and then remove from the stove.
Fill a saucepan with plenty of water and bring the water to a boil. When the water boils, add the udon noodles and cook while stirring (e.g. with a chopstick). After the water has boiled again, pour the udon noodles into a strainer and allow to drain.
Put the noodles in bowls and top with kamaboko and spring onions. Pour the broth over them.