Put the milk in a double boiler; when hot add the butter. Let the milk boil; then add the flour, and beat it hard until it leaves the sides of the pan; then remove from the fire and stir in gradually the eggs, which have been well beaten, the yolks and whites together, and a dash of salt. Continue to beat the batter until it is no longer stringy. Turn it into a warm greased pudding-dish, and bake in a moderate oven thirty to thirty-five minutes. It should puff up like a cream cake, and have a thick crust. Serve as soon as it is taken from the oven, or it will fall. The batter may stand some time before baking if convenient. It may be baked in gem-pans fifteen to twenty minutes if preferred. Serve with plain pudding or hard sauce.