Scald the milk, and add the butter, sugar and salt. When it has become lukewarm, add the yeast dissolved in a quarter cupful of lukewarm water. Stir in enough flour to make a drop batter, cover it well, place it in a warm place free from draughts, and let rise over night. In the morning stir it down, grease some muffin-rings, place them on a hot greased griddle, fill the rings half full of batter. It will rise to the top. Turn the muffins with a pancake turner and bake them on both sides until a thin brown crust is formed. Two eggs may be added to the batter in the morning if desired. If so, beat the yolks and whites separately and add the whites last.