For the hot chocolate with rum grate the chocolate.
Heat the milk in a saucepan, add a pinch of vanilla sugar and melt the chocolate in it.
Whip the cream with a pinch of sugar until stiff.
Pour the chocolate milk into heat-resistant glasses, add a spoonful of rum to each and place a whipped cream topping on top.
Serve the hot chocolate with rum sprinkled with cocoa.