Wash and dry 1 kg (2¼ lb) mushrooms, peel them if necessary then pass through a coarse sieve.

Melt 60 g (2 oz) butter in a shallow pan, add the mushroom purée and cook quickly until all the moisture has been evaporated.

Add 3 dl (½ pt or 1¼ U.S. cups) Sauce Béchamel which has previously been reduced with 1 dl (3½ fl oz or ½ U.S. cup) cream; season with salt, pepper and a little grated nutmeg and reduce on a hot stove.

Remove from the heat and finish with 100 g 3½ oz) good butter.