How long can I leave marzipan on the Time-Honoured Christmas cake before I set about royal icing it? Haven't made a Christmas cake in years and can't see any advice in my many cook books on this question.
Rich fruit cakes, such as Nigella's Time-Honoured Christmas Cake (from FEAST) are usually covered with a layer of marzipan before they are iced. The marzipan helps to keep in moisture, prevents colour from the dried fruits seeping into the icing and provides a smooth surface to ice on.
We would suggest icing the cake about a week before Christmas if you want to avoid a last minute rush. Cover the cake with marzipan and then if possible let the cake stand for 24 to 48 hours so that surface of the marzipan can dry out. This gives a firmer surface for icing but also reduces the risk of any of the oils from almonds in the marzipan staining the white icing. If you are using royal icing you may prefer to use powdered egg white or meringue powder instead of fresh egg white. If you live in the UK you can also buy royal icing sugar, which has powdered egg white already added and easy to follow mixing instructions.