Classic Cream of Chicken Soup

Heat the butter in a saucepan. Add the leeks, celery and garlic. Sauté very gently for several minutes, making sure nothing takes on any colour, until the leeks are translucent and soft. Pour in the chicken stock and the milk. Add the sprig of tarragon and season with salt only. Simmer very gently for around 15 minutes. Remove from the heat and allow to cool slightly. Fish out the tarragon sprig and transfer the soup to a blender.

Cut up the chicken and add it to the blender. Blitz until very smooth. (You can also put this through a sieve if you like, to make it even smoother.) Return the soup to the saucepan and heat gently. Grate in a little nutmeg and some very finely ground white pepper. Whisk the cream with the egg yolk until smooth. When the soup is heated through (piping hot to serve), remove it from the heat and, in a slow, steady stream, add the cream and egg yolk mixture, stirring or whisking until it has completely combined with the soup. Serve immediately.

the flavours above are quite delicate. You can make it much more robust by adding woodier, more pungent herbs such as thyme to the broth, or spicier by making up a bouquet garni with a few cloves, a piece of mace and some crumbled pieces of bay leaf. There is also a German version of this, flavoured with caraway. Add bay, sprigs of parsley and thyme to the soup with 1 tsp caraway seeds and just make sure you sieve it well after you have blended it. Finally, another favourite combination of mine involves chopped tarragon and basil leaves and 1 tsp of finely grated unwaxed lemon or lime zest mixed in at the end. It injects a little bit of freshness without becoming overpoweringly citrusy.