method
1. Break the chocolate into squares and place them in a basin. Stand the basin over a saucepan of simmering water and leave until the chocolate has melted, stirring occasionally.
2. Remove the basin from the heat and stir in the butter, orange rind and Cointreau.
3. Mix in the egg yolks. Whisk the whites until stiff, then fold into the chocolate.
4. Spoon the mousse into individual dishes and chill for at least 1 hour.
5. Decorate with chocolate curls, if used, and serve with crisp dessert biscuits.
