Japanese-style vegetable soup

Peel the turnip, carrots and blach salsifies and cut them into 2 mm thick slices. Cut off the stems of the shiitake mushrooms and halve or quarter them. Wash the spring onions and cut them into thin strips. Dice the tofu. Heat up the sesame and soybean oil in a pan. Heat the oil to a high temperature and fry the turnip, carrots, salsifies and shitake mushrooms briefly. Add the vegetable stock (or water) and bring to the boil (skim just before it reaches boiling point). Season the liquid with soy sauce and sugar. Mix the corn starch and water in a bowl and use it to thicken the liquid. Then, add the tofu and spring onions before bringing the soup to the boil again.