The Irish Pub Cookbook says a similar mousse using Guinness is served at the Guinness Storehouse at St. James' Gate in Dublin. Top it with a white chocolate mousse for a look-alike of a creamy pint.
WHITE CHOCOLATE LAYER: In a small saucepan over medium heat, combine the white chocolate and 1/2 cup of the cream. Stir until the chocolate has melted and the mixture is smooth. Remove from the heat and let cool, stirring once or twice, for 30 minutes or until thickened. In a small bowl, beat the remaining 1/2 cup of cream with an electric mixture until stiff peaks form. Fold the whipped cream into the white chocolate mixture. Spoon the mixture over the top of the chocolate mousses and refrigerate for at least two and up to 24 hours.