In a small saucepan, gently heat milk over low heat. Whisk often so the milk doesn’t burn.
While the milk is heating, bring a medium saucepan with two inches of water to a boil. Place a heat-proof bowl with chocolate pieces over the simmering water. Make sure the bottom of the bowl does not touch the simmering water. You’re creating a double boiler. Cool, right? Stir the chocolate pieces until melted.
Add the melted chocolate to the hot milk. Whisk together until completely blended and super delicious looking. Pour into mugs and top with marshmallows or slightly sweetened whipped cream.