Rub the chicken breasts with drops of lemon juice and sprinkle lightly with salt and pepper. Heat the butter in a heavy, oven-proof casserole, about 10 inches in diameter until it is foaming. Stir in the minced shallots or green onion and saute a moment without browning. Then stir in the mushrooms and saute lightly for a minute or two without browning. Sprinkle with salt.
Quickly roll the chicken in the butter mixture and lay a piece of buttered wax paper over them, cover casserole and place in hot oven. After 6 minutes, press top of chicken with your finger. If still soft, return to oven for a moment or two. When the meat is springy to the touch it is done.
Remove the chicken to a warm platter (leave mushrooms in the pot) and cover while making the sauce (2 to 3 minutes).
To make sauce, pour the stock and wine in the casserole with the cooking butter and mushrooms. Boil down quickly over high heat until liquid is syrupy. Stir in the cream and boil down again over high heat until cream has thickened slightly. Off heat, taste for seasoning, and add drops of lemon juice to taste. Pour the sauce over the chicken, sprinkle with parsley and serve immediately.