Peel and cut up the onions and fry for 3 minutes in a little butter. Clean the mushrooms with a damp cloth, cutting away buggy stems, then add them to the onions. Add the milk and bring it slowly to the boil in a large pan, making sure that it does not boil over. Add the leaves from the thyme sprigs and a little pepper and salt. Leave to simmer gently for an hour or more, and then thicken with a little cornflour paste prepared with water. Adjust the seasoning and serve with croutons cooked in butter and flavoured with a little thyme.
This is how my grandmother, Sarah, served them day after day in season and I still love them this way.
© 1986 All rights reserved. Published by Macmillan.