Ingredients:
1 grouper head, plus 100-120g grouper fillet (if you can't get grouper, use salmon)

Half a 496g packet of firm tofu (optional)

Half a leek

20g Chinese leaf, cut into 2cm strips

20g beansprouts

2 fresh shiitake mushrooms cut into 1cm slices

3 tbsp soy sauce

1cm root ginger, grated

5cm mooli, grated

Method:
Grouper is full of collagen and, for that reason, it is expensive in Japan and the food of the rich and famous. It is economical in the west, though. You can of course omit the fish head, but you will lose a lot of collagen if you do. I promise you, it's worth it.

Put the fish head and 500ml of water in a large pan. Bring slowly to the boil, then reduce the heat, cover and simmer for 15 minutes. Remove and discard the fish head. At this point, you may chill, or freeze, the soup base in cubes. It will be extremely low in calories in this ungarnished state.

Cut the tofu (if using) into two centimetre cubes. Cut the leek into three centimetre chunks, then cut these into lengthways strips.

Return the fish stock to the boil, then add the grouper fillet, tofu, leek, Chinese leaf, beansprouts and shiitake mushrooms. Cover and cook over a medium heat for 10 minutes.

Uncover and add the soy sauce, ginger and mooli. Serve immediately in warmed bowls. Serves two: 420kcal in total, 210kcal per bowl.