1. Place the chocolate in a medium heatproof bowl. Place over a saucepan of simmering water and stir occasionally until the chocolate melts. Remove the bowl from the pan and stir in the egg yolks and liqueur.
2. Use electric beaters to whisk the egg whites in a medium, clean, dry bowl until soft peaks form. Add the sugar and whisk until thick and glossy. Using a large metal spoon fold a spoonful of the egg white mixture into the chocolate mixture. Fold in the remaining egg white mixture until evenly combined.
3. Use the beaters again to to whisk the cream until soft peaks form....then fold into the chocolate mixture until evenly combined.
4. Spoon the mousse into 8 serving dishes and cover with cling wrap and pop into the fridge for at least 2 hours or until well chilled. (Note: this recipe takes a little longer to set because of the liqueur.
