Choose a pound of fine, sound, large, fresh mushrooms, neatly pare off the ends, clean, and wash them well. Drain, and place them in a sautoire with an ounce of good butter. Season with a pinch of salt and half a pinch of pepper. Cover, and let them cook for ten minutes, tossing them well meanwhile. Squeeze in the juice of half a medium-sized sound lemon; add a pinch of chopped parsley, nicely sprinkled over. Place six pieces of toasted bread on a hot dish, dress the mushrooms over the toasts, and serve.