Birthday Custard Sponge Icing

Our answer

Nigella's Birthday Custard Sponge (from Feast and on the Nigella website) is a Victoria sponge cake with a buttercream filling that has extra yellow colour and vanilla flavour provided by custard powder. It is topped with a chocolate icing.

The golden syrup is part of the icing mixture and is used to provide some additional sweetness but also to help to keep the icing soft. As the icing contains dark (bittersweet) chocolate it can set fairly firmly. Adding the syrup helps to keep the icing slightly softer as it is hygroscopic and so attracts and retains moisture. If you don't have any golden syrup then honey would be a good substitute, though try to use a very mild honey so that the flavour of the honey does not affect the icing. You could also use light corn syrup or glucose syrup as alternatives. If you don't have custard powder then in the cake replace it with 3 tablespoons of cornflour (cornstarch) and 2 teaspoons of vanilla extract and for the buttercream replace it with 4 teaspoons of cornflour and 3/4 teaspoon of vanilla extract. Add a couple of drops of yellow food colour to the cake batter and buttercream if you want a slightly richer yellow colour to the cake.