Puree the apricots in a blender or food processor.
Put the egg yolks into a bowl and beat, adding the sugar gradually.
Continue beating until the mixture is thick, pale and mousse-like.
Fold in the apricot puree.
Whip the cream, adding the grated orange rind and liqueur.
Beat the egg whites until stiff.
Fold the whipped cream into the apricot mixture.
Lastly, using a large metal spoon, fold in the egg whites gently but thoroughly.
Spoon the mousse into a freezerproof container or serving dish and freeze until firm.
Transfer the mousse to the refrigerator just before serving the first course, to allow the dessert to soften.