Japanese
Bring the dashi to a simmer in a large pot and season with soy sauce and mirin to make the broth.
Cook the udon noodles in a separate pot of boiling water according to the package, then drain.
Divide the hot noodles between two deep bowls.
Ladle the hot broth over the noodles.
Top with sliced fish cake, a soft-boiled egg or a piece of prawn tempura, and spring onions.
Serve immediately while piping hot.