For each cup cocoa, mix ½ to 1 Tablespoon Sugar, 1 Tablespoon cocoa, and ¼ cup water. Cook over low heat (boil about 1 minute), stirring constantly. Add ¾ cup milk. Heat until scalded, but do not boil. Add a pinch of sale (a drop of vanilla, too, if desired). Just before serving, beat with rotary beater. Serve hot.. pour over a marshmallow in each cup.