Mushroom Sauce ( to serve with Beefsteaks, Fillets of Beef, etc. ).
Having prepared the mushrooms by cutting off the stalks, and if they are large, by cutting them in halves or quarters, throw them into a little boiling water, or, what is much better, stock. Do not use more than is necessary to cover them. This must be seasoned with salt, pepper, and a little butter. Boil the mushrooms until they are tender, then thicken the gravy slightly with a roux of butter and flour. Add a few drops of lemon-juice. It is now ready to pour over the meat.