Sheet Cake Icing Still Runny

Our answer

Nigella's Chocolate Sheet Cake has a tender chocolate sponge cake topped with a fudgy chocolate icing. The icing is poured over the sponge while it is still warm, so some of the icing soaks into the cake. The sponge stays fairly moist because of this, so we wonder if the texture of the sponge was just slightly different to expectations. If the sponge didn't rise then check that the bicarbonate of soda (baking soda) has not gone past its best before date. Also as bicarbonate of soda acts quickly you need to make sure that the cake batter goes into the preheated oven as soon as it has been mixed.

The icing usually sets quite quickly though it does not set solid but has a slightly soft consistency. If it is very warm weather then the icing may take longer to set so putting the cake into the fridge for an hour or so may help the icing to set. Store the cake in a cool place, particularly in hot or humid weather.