Clear clam soup (Asari no ushiojiru)

1. Soak the clams in 3% salted water in a dark place for 1 hour to purge the sand, then rinse under running water, rubbing the shells together; discard any that are open and don't close when tapped.

2. Put the kombu in a pot with the cold water and soak for 20 minutes.

3. Add the clams and heat slowly over medium heat; remove the kombu before it boils.

4. As soon as the clams open (3-4 minutes), skim off the foam and add the sake.

5. Taste: add at most a pinch of salt to the clams' salty broth, and discard any that stay closed.

6. Ladle into small bowls and serve with sliced spring onion and mitsuba leaves.

Tip: "Ushio" means seawater: this soup relies almost entirely on the clams' own flavour, so there's no soy sauce. Parsley leaves can stand in for mitsuba, with a similar fresh green taste.