Cut the chocolate in small pieces.
Pour the sugar and the whip cream in a casserole and let it boil.
Take away the casserole from the stow and pour in almost all the chocolate and stir until it is melted.
Place the mixture in the fridge until it is cold.
Take out the mixture from the fridge and mix it with an electrical mixer on high speed.
Place the mousse in small portion size bowl.
Serve directly if you like to have a fluffy mousse. Or place the mousse in the fridge again if you prefer a more compact mousse and take it out right before it is time to serve it.
Decorate the mousse with the rest of the chocolate.