Cook the noodles according to the packet instruction, drain and keep warm.
Finely chop the carrot and salad onions.
Heat the vegetable stock in a saucepan, add the carrot pieces and cook for 3 minutes.
Add the peas and cook for another 2 minutes.
Add the wakame, cook for another 3 minutes or so.
Meanwhile, mix the miso, soy sauce and mirin or rice vinegar in a small bowl with a spoonful of the stock and make a smooth paste.
Turn off the heat. Add the salad onion pieces, mint leaves and the miso mixture to the soup.
Add the noodles. Reheat if necessary.
Serve warm with sesame seeds and mint leaves scattered on top.