Warm the milk in a small saucepan. Break off 2 corners of the Toblerone and set aside. Chop the rest of the chocolate and melt it in a hot water bath. Slowly pour in the milk, stirring constantly, allow to cool.
In the meantime, whip the cream until stiff and then fold it into the still liquid chocolate.
Cover and chill the mousse for at least 4 hours.
With the help of 2 spoons, cut off the mousse and serve in glasses.
Grate the rest of the Toblerone over it with a peeler.