Chocolate Fudge Sheet Cake

Our answer

Nigella's Chocolate Fudge Cake (from NIGELLA BITES) is a 20cm/8-inch layer cake. Normally to convert from a round cake to a square cake you would reduce the pan size by 2cm/1 inch, but as the conversion is to be for a single layer cake only, which would require a slightly deeper layer of cake, we suspect that you would need to change to a 23cm/9-inch square cake pan or a 17x28cm/7x11-inch rectangular pan. The pan should be at least 4cm/1½ inches deep and the cake batter should come no more than two-thirds up the side of the pan. We would also suggest lining the pan so that the baking parchment (parchment paper) comes up the sides of the pan. This will make it easier to remove the cake when it is cool.

The cake batter is quite liquid and the baking time for the layers is quite long, so it is slightly tricky to give definitive baking times but use the same oven temperature and we would suggest initially baking the cake for 50-55 minutes and carefully checking it to see if it is done, but don't open the oven door at least until the top looks risen and set (otherwise the cake may sink). If you can, carefully give the pan a half turn after the initial baking time (if it is not quite done) as the sharp corners of the cake will colour more easily. The cake is done when it is firm to the touch, shrinking away slightly from the edges of the pan and a cake tester inserted into the centre comes out clean. You may not need all of the frosting, so we would suggest making two-thirds to three-quarters of the frosting for a generous top coat. We would also mention that as we have not tried the cake in this format, we are unable to guarantee the results.