I would like to use Nigella's Buttermilk Birthday cake for a Wilton butterfly cake tin for my child's upcoming birthday (am trying to avoid the temptation of purchasing the cake as I have done for all previous birthdays!). The tip sheet for the tin instructs to make one 2-layer cake mix and I am not sure how to convert this for Nigella's receipe (I am a complete novice when it comes to baking!). So will the receipe as it is be equivalant to a 2-layer cake mix? Or do I need to make two lots of the buttermilk birthday cake mix, and then fill the cake tin with the combined mixture? If doubling the contents in this way, does it then need longer cooking time? (the tip sheet for the tin suggests 30-40 min and I assume that is for a non-fan forced oven). Is it better to bake using fan forced or non-fan forced? I was planning on freezing the cake - would this be ok?
The introduction to Nigella's Buttermilk Birthday Cake (from Domestic Goddess, p210) gives some information on how to convert this recipe for a shaped cake tin. Nigella has suggested that you make a double quantity of the cake mixture for a shaped tin. You wlll find that you have a bit too much batter as the tin should be filled to just over half full (and no more than 2/3 full) but it is difficult to scale down the cake batter by a small quantity. Instead bake the extra batter as cupcakes (at 180c/350F for around 20 minutes).
The cake should be baked at 180c/350F and Nigella writes that she usually finds that the shaped mould needs about 45 minutes. As all ovens vary we would suggest starting to check the cake after 35 minutes; once cooked the cake should be firm to the touch, slightly shrinking away from the sides of the pan and a cake tester inserted into the centre should come out clean. If it is not cooked then bake for another 5 minutes and carefully check again. You can use a conventional or fan forced oven but please note that Nigella's oven temperatures are for conventional ovens and you should check your oven handbook for a fan forced oven as it may require some adjustment.
You can freeze the baked cake, though with larger cakes be careful to make sure that it won't be damaged in the freezer. Wrap the fully cooled and unmoulded cake in a double layer of clingfilm (plastic wrap) and a layer of foil. As the cake is quite large we would suggest freezing the wrapped cake on a large baking sheet until it is fully solid, and make sure that the cake is on a flat surface, or suitably supported, when it is in the freezer. You can freeze the cake for up to 3 months and to thaw the cake unwrap it and leave it on a wire rack at room temperature for 3 to 4 hours.