Mince the onion and cut the vegetables into bite-sized pieces. Heat sesame oil in a pot, sauté the vegetables until cooked, then remove and set aside.

Add sesame oil to the pot, sauté the minced onion until softened. Add water and chicken stock powder, bring to a boil, then dissolve miso into the mixture.

Add soy milk to the soup base and bring to a boil. Add somen noodles and cook for about 4 minutes, stirring occasionally.