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 cocoa 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. Add the salt, to taste.
Pour into mugs and top with marshmallows, whipped cream, or stick a peppermint stick in there!
Notes
You can go as basic or as fancy as you like with the chocolate. Nothing wrong with some bagged semi-sweet chocolate chips, whether a store brand or something tonier. If you have a favorite semisweet or perhaps bittersweet chocolate bar, try using it here. When a high-end chocolate bar lands in my kitchen during the cold months, this is a nice way to stretch it into a hot chocolate treat for a group.