- 25 g dried kombu
- 1 tablespoon sake, Chinese rice wine or dry sherry
- 2 teaspoons caster sugar
- ½ teaspoon finely grated fresh ginger
- 1½ tablespoons miso
- 4 spring onions, sliced
- 6 fresh shiitake mushrooms, thinly sliced
- 85 g tofu, diced
- 3 cups trimmed watercress, about 85 g
- Put the kombu in a saucepan and pour in 1 litre of water. Bring slowly to the boil, then remove from the heat and cover the pan. Set aside for 5 minutes. Use a slotted spoon to remove and discard the kombu.
- Stir the sake, rice wine or sherry, sugar and ginger into the broth and return to the boil. Reduce the heat and stir in the miso until it dissolves completely.
- Add the spring onions, mushrooms, tofu and watercress. Cook very gently, stirring, for 2 minutes without allowing the soup to boil. Ladle into small bowls and serve at once.
- Kombu is a sun-dried edible seaweed that is very popular in Japanese cookery. Wipe the surface with a damp cloth before using. It can be finely shredded or snipped into fine strips with scissors and returned to the broth, if you like, to add an interesting texture contrast.
- Miso is a fermented paste made from soya beans. If your supermarket does not stock it, try a health-food store.
- For an intense herb flavour, add 1½ tablespoons finely chopped fresh coriander leaves with the watercress.