Allow to cool until the chocolate no longer feels hot to the touch. Beat the butter in a bowl until soft, then gradually beat in the icing sugar. Add the vanilla extract and beat again.
To make the icing: Break the chocolate into small pieces and add to a pan to heat up. Add the double cream and melt the mixture over the lowest heat setting. Stir the icing until smooth ...
Cook, stirring occasionally and ... Pipe a 1/2-inch-tall border of icing around edge of first cake layer. Spoon half of chocolate mousse (about 2 cups) onto center of cake, and spread evenly ...