Cut off the ends of the stalks, and pare neatly some middle-sized or button-mushrooms, and put them into a basin of water with the juice of a lemon as they are done. When all are prepared, take them from the water with the hands to avoid the sediment, and put them into a stew-pan with a little fresh butter, white pepper, salt, and a little lemon-juice; cover the pan close, and let them stew gently for twenty minutes or half an hour; then thicken the butter with a spoonful of flour, and add gradually sufficient cream, or cream and milk, to make the same about the thickness of good cream. Season the sauce to palate, adding a little pounded mace or grated nutmeg. Let the whole stew gently until the mushrooms are tender. Remove every particle of butter which may be floating on the top before serving.