Melt the dark chocolate in a small saucepan over low heat. Remove from heat and allow to cool. In a bowl, beat the egg yolks and stir in the melted chocolate and Irish cream. Fold in 1/2 of the whipped cream.
In a separate bowl, beat the egg whites until stiff. Fold the egg whites into the chocolate mixture. Pour the mousse into serving glasses and garnish with remaining whipped cream and chocolate shavings before serving.