Chocolate Guinness Cake Sinking

Our answer

Nigella's Chocolate Guinness Cake (from Feast and on the Nigella website) is actually more similar in structure to a sticky gingerbread cake than to a sponge cake. This means that it will be slightly denser and moister in texture than a sponge cake.

The cake has bicarbonate of soda (baking soda) as the only raising agent. Bicarbonate of soda is quite active so make sure that you measure the amount carefully as too much will cause the cake to rise up too much during baking and then fall back on cooling. The oven should also be preheated properly before you mix the cake as the batter needs to go into the oven as soon as it is mixed, otherwise the bicarbonate of soda can run out of "fizz" and the cake won't rise enough. Bicarbonate of soda also needs an acid ingredient in the batter to work properly and sour cream is the main acid ingredient. If regular cream is used instead then this may not be acidic enough for the bicarbonate of soda to produce the carbon dioxide needeed to cause the cake to rise.

The cake can sometimes sink if it is not baked enough and for this cake you should carefully and gently press the centre of the cake with your fingertips - it should be firm to the touch if fully cooked. The sides of the cake may also be shrinking away slightly from the side of the tin. A cake tester may have some crumbs of cake on it when inserted to the centre of the cake, as it is a damp cake, but the crumbs should not be wet and there should not be any traces of uncooked cake batter. As all ovens vary slightly you may find that the cake needs slightly more (or less) baking time that the time stated in the recipe.