Crumble the chocolate. Heat in a small saucepan with 100 ml of cream over low heat until the chocolate has melted, then allow to cool. Add the rum and stir the cream with a whisk. Beat the rest of the cream with icing sugar until stiff. Carefully fold the chocolate mixture into the cream so that a striped pattern remains.
Pour the cream into two bowls and chill. Serve sprinkled with chocolate flakes.