Combine the water, cocoa powder and sugar in a medium saucepan, and place over medium high heat. Bring to a boil, whisking frequently, and then continue to whisk until the sugar and coca powder are dissolved. Reduce the heat to medium and whisk in the milk. Bring to a simmer whisking very frequently. Add the chopped chocolate and whisk until the chocolate is melted and everything is smooth.
Pour into mugs and topped with marshmallows, whipped cream, or stick a peppermint stick in there!