Chilled Lemon Grass and Coriander Vichyssoise

First of all, strip the coriander leaves from the stalks and reserve both the leaves and the stalks.

Lemon grass is dealt with in exactly the same way as leeks: that is, you trim the root and the tough top away, leaving about 6 inches (15 cm) of stem, remove the outer skin and chop the lemon grass quite finely. Then do the same with the spring onions. Next, gather up all the trimmings from both, wash them and pop them into a saucepan together with the coriander stalks, some salt and 1½ pints (850 ml) water and simmer (covered) for about 30 minutes to make a stock.

To make the soup, melt the butter in a large saucepan, then add the chopped lemon grass, onions (reserve the spring onions till later) and potatoes and keeping the heat low, let the vegetables sweat gently (covered) for about 10 minutes. After that, pour in the stock through a strainer, discard the debris, then add the milk and about three-quarters of the coriander leaves. Season with salt and pepper, bring the soup up to simmering point and simmer very gently for about 25 minutes.

Allow the soup to cool a little before pouring it into a food processor or blender, whiz it up, then pour it through a strainer into a bowl. When it's cold, cover and chill thoroughly till you're ready to serve.

I think it's a good idea to serve the soup in glass bowls that have already been chilled. Add a cube of ice to each bowl and sprinkle in the rest of the coriander (finely chopped) and the spring onions as a garnish. Finally, float some lemon slices on top and serve straight away.