Whip the cream until soft tips form (not quite firm, but firm enough to spoon).
Carefully heat the milk in a saucepan and add the chocolate, broken into small pieces. Melt the chocolate while stirring until a uniform mass is formed. Now heat the chocolate milk until just before it boils. Take the pot off the stove.
Put 5 mini marshmallows in each mug and pour the hot chocolate milk over them.
Distribute the whipped cream between the 2 cups and dust with a pinch of nutmeg.
If you want, you can serve a mikado stick to start stirring.