Prepare the leeks, removing the outer layer and trimming off the ends; use both the white and the tender green parts. Wash very thoroughly and cut into thick rings.

Trim and wash the courgettes; slice into thick rings. Place the vegetables in a large saucepan with 2 3/4 pints (1.6 litres) water and the 2 crumbled stock cubes.

Bring to the boil, cover and simmer over a low heat for 50 minutes. Turn off the heat and beat with a hand-held electric beater until smooth, or put through a blender or vegetable mill; return to the pan and reheat briefly. Add salt and freshly ground white pepper to taste and stir in the parsley.

Ladle into soup bowls. Pour the cream in a very thin stream into each bowl to form concentric circles then draw the tip of a spoon from the centre outwards across the circles to give an attractive spider's web effect and serve hot or chilled.