Select very small fresh flap mushrooms, blanch them for 7–8 minutes in boiling water then drain and cool. Place in an earthenware Terrine and cover with a boiling marinade made as follows:
Proportions for 1 kg (2¼ lb) of flap mushrooms: 5 dl (18 fl oz or 2¼ U.S. cups) vinegar; 1½ dl (5 fl oz or ⅝ U.S. cup) oil, 10 g (⅓ oz) crushed garlic, a little thyme and crushed bayleaf, 6 peppercorns, a pinch of coriander and fennel and a small root of parsley. Bring to the boil and simmer very gently for 10 minutes beforé passing through a strainer over the flap mushrooms.
Allow to marinate for 8 days then serve with a little of the marinade.