Old Fashioned Chocolate Cake Traybake

Our answer

Nigella's Old Fashioned Chocolate Cake (from Feast and on the Nigella website) is a popular sponge cake and is usually made as a round layer cake. In theory it would be possible to convert it to a single layer rectangular or square cake (a traybake) but the conversion is not straightforward as you woud not want the traybake cake to rise too much in the pan on baking, in the same way that a sandwich or layer cake would. Also traybake cakes often have a slightly more robust cake structure. Traybakes are however popular for school summer fairs and birthrday cakes for school as they are easy to divide up and eat.

Our best guess, and we would very much emphasise that we have not tested this so cannot guarantee the results, is that you would need about 3/4 of the cake recipe and bake the cake in a 23cm (9-inch) square tin. The batter should come approximately 1/4 to 1/3 of the way up the tin before baking. You are likely to need about half of the icing quantity as you will only be icing the top of the cake. However we would very much recommend that you look at Nigella's Chocolate Sheet Cake recipe (on the Nigella website) as this is a very good traybake and very easy to make. If you are cooking for a school fete or summer fair then Domestic Goddess has a section of suggestions (p235), including Millionaire's Shortbread and some mini versions of popular cakes.