I love dark chocolate and used a 75% Lindt bar for this one.
Quick to prepare, and although you have to wait for a few hours for it to set, it's worth the wait.
Cooking time is actually chilling/setting time.
Melt the chocolate over a bain-marie until smooth.
Beat the egg whites to soft peaks, sprinkle the sugar, and continue beating to a stiff meringue, a minute or two longer.
Beat the yolks with the orange zest in a bowl.
Whisk the chocolate into the yolks.
Fold in a spoonful of the whites into the chocolate mixture.
Pour the chocolate into the remaining whites and fold gently to combine evenly.
Pour the mousse into 8 serving bowls. Wrap well with plastic, and refrigerate at least a few hours. Serve garnished with whipped cream, chocolate shavings, and a little orange zest.