Heat the milk in a medium-sized saucepan over medium heat. When the milk is warm, remove it from the heat and whisk in the chocolate, stirring until it is melted. Return to the heat and cook at a very low boil for about 2 to 3 minutes, whisking constantly. Serve warm in demitasse cups or small mugs with a splash of peppermint Schnapps (optional), and/or topped with marshmallows and a sprinkle of peppermints.