The Japanese are really fond of shellfish, and clams are among the most popular. In season, they become sweet and juicy, and are excellent with this sweet-and-sour dressing.
If using fresh clams or cockles, wash the shells under running water. Discard any that remain open when tapped.
Pour 1cm/½in water into a small pan and add the clams or cockles. Sprinkle with the sake, cover, then bring to the boil. Cook over a vigorous heat for 5 minutes after the water reaches boiling point. Remove from the heat and leave to stand for 2 minut