Why Does My Chocolate Guinness Cake Sink?

Our answer

Nigella's Chocolate Guinness Cake (from FEAST) is made using the "melt and mix" method, where the butter and Guinness are melted together and then the remaining ingredients are added. This tends to give quite a liquid cake batter and it can take longer to cook than a regular sponge, particularly as it is a fairly deep cake. The recipe suggests 45 minutes to 1 hour of cooking time, but as ovens vary it can take longer. Generally, if a cake sinks in the centre then it is usually not quite cooked through and needs slightly longer cooking time. The cake should feel firm on top if you press it lightly with your finger, a cake tester should come out clean (or with a couple of cooked cake crumbs attached) and the cake will be slightly shrinking away from the sides of the pan.

If the cake comes out of the oven with a big peak in the centre then it can also indicate a couple of possible problems. The oven may be running too hot, which causes the outsides of the cake to cook too quickly, pushing up the centre of the cake but leaving it undercooked. The cake will then sink as it cools. In this case, you may need to reduce the oven temperature by 20c (50F) and cook for slightly longer. A very risen cake that sinks drastically on cooling can also be a sign of too much bicarbonate of soda (baking soda), particularly if the cooled cake has a wrinkled surface. The cake uses 2 1/2 teaspoons of bicarbonate of soda and these should be measured carefully using a standard measuring teaspoon (5ml) and half teaspoon (2.5ml). They should always be level measures. If there is too much bicarbonate of soda then the cake expands rapidly in the oven but this over-stretches the glutens in the flour and they can't maintain the structure when the cake starts to cool, causing it to sink. So measure the bicarbonate of soda carefully and only use plain (all-purpose) flour.