I made and iced the chocolate Birthday Cake (from How to Eat) with chocolate ganache, but the party has been cancelled! Can I freeze it?
Nigella's Birthday Cake (from HOW TO EAT) is a rich and dense chocolate sponge cake that is sandwiched and coated with a ganache icing (a mixture of chocolate and cream). The sponge and icing both freeze separately but generally we do not recommend freezing already iced cakes as they do not freeze quite as well when assembled and may not last as long in the freezer.
In this particular situation, rather than waste the cake you could freeze it but you would need to put the cake on a board or baking sheet lined with baking parchment (parchment paper) and freeze it, uncovered, until solid. Then wrap the cake in a double layer of clingfilm (plastic wrap) and a layer of foil and store in the freezer for up to one month. To thaw the cake, unwrap it and put it on a serving plate, then leave at cool room temperature for about 6 hours. However we would mention two things about the ganache. The first is that the ganache will lose some of its shine and glossy appearance when it defrosts. The second is that the ganache may not set fully when frozen, this will depend on the chocolates used. If you have used all dark (bittersweet) chocolate then the ganache should freeze firm. But of you have used part dark chocolate and part milk chocolate then the ganache may stay a little soft when frozen. It depends on the amount of milk chocolate used and also the quality of the milk chocolate. The ganache will be fine to eat but may have marks on it where the cake has been wrapped.