Is there a way to make the vanilla Birthday Custard Sponge by hand? How long should I beat the cake batter for?
Nigella's Birthday Custard Sponge (from FEAST) is similar to a Victoria sponge cake but the vanilla flavour and yellow tint come from the addition of custard powder. The method suggests mixing the sponge cake ingredients in a food processor until they form a smooth batter and this should only take a minute or two. If you make the cake with a mixer, or by hand with lots of elbow grease, then you need to beat the sugar and butter together thoroughly until they are pale and look slightly fluffy. This is likely to take 3 to 4 minutes with an electric hand mixer. Next beat in the eggs, one at a time. Each time beat the mixture until the egg has been completely mixed in before adding the next egg. If the mixture looks like it is curdling at this stage then add a tablespoon of the flour with each egg. Whisk or sift together the flour, custard powder, baking powder and bicarbonate of soda (baking soda) and using a very low speed mix this into the butter and egg mixture. Gently mix in enough milk to give a batter that falls slowly off a mixing spoon. Once the flour has been added to the cake you need to mix the cake batter as little as possible, as mixing develops gluten in the flour and will mean that the cake has a less tender texture.
Custard powder is easy to buy in the UK but if you can't find it then use 2 tablespoons of cornflour (cornstarch) instead and add 1 teaspoon of vanilla extract when you beat in the final egg.