Cook the noodles according to the packet instruction, then drain and keep warm. This should take about 5 minutes.
Heat the vegetable stock in a saucepan, add the edamame beans and cook for 5 minutes.
Add the seaweed, cook for another 3 minutes or so.
Meanwhile, mix the miso, soy sauce and rice vinegar in a small bowl with a spoonful of the soup and make a smooth paste.
Turn off the heat. Add the chopped spring onion pieces and the miso mixture to the soup.
Add the noodles. Reheat if necessary.
Serve with sesame seeds scattered on top, if liked.