Trim the ceps carefully, cutting out any damaged parts. If the caps are slightly slimy, scrape with a sharp knife and remove the tubes underneath the cap.

Scrape the stalks and cut off the ends. Wash the ceps in cold water and drain them well. Halve or quarter larger ceps, leaving small ones whole.

Melt the butter in a large frying pan, add and fry the onion until golden. Add the ceps and braise them, stirring continuously. Gradually pour in the hot stock, cover the pan and cook for 10 - 15 minutes. Season to taste.

Beat the egg yolks into the cream. Remove the ceps from the heat and stir in the egg yolk and cream mixture. Warm through for a few minutes, but do not allow to boil. Serve sprinkled with parsley.