Butter a springform pan.
Heat the cream, chocolate, butter, and sugar in a saucepan until the chocolate has melted completely. Beat the eggs, orange juice, and rum in a large mixing bowl and fold in the chocolate mixture. Spread into the prepared pan and bake in a preheated oven at 180°C (approximately 350°F) for 40 minutes. Remove from the oven, let cool in the pan. Remove from the pan and set overnight in the refrigerator.
Loosen the cake from the mold, spread with the chocolate frosting, sprinkle with white chocolate shavings and dust with powdered sugar. Serve as desired.