Cook the noodles according to the instructions on the packet until just tender. Drain, rinse in cold water and drain again.
Whisk the soy sauce with the mirin, sesame oil, wasabi paste and sunflower oil in a bowl until well blended. Add the noodles and toss gently to coat evenly, then stir in the spring onions and toss to mix well.
Divide the noodles into 20 bite-sized portions and twirl each portion with a fork to make a neat nest. Carefully transfer to individual oriental soup spoons, then, using a teaspoon, top each nest with a little tobiko or salmon roe and serve immediately.