Birthday Cake

Method

1. Heat the oven to 180C (160C fan). Butter a 12 cm round cake tin and line the base with a disc of baking paper. Have all the sponge ingredients at room temperature so the batter emulsifies rather than splits.
2. Put 45 g of very soft unsalted butter and 45 g of caster sugar in a bowl and beat with electric beaters or a wooden spoon for 3-4 minutes, scraping down once, until the mixture is noticeably paler, light and fluffy.
3. Break in 1 large egg, add 0.25 tsp of vanilla extract and beat hard for 1 minute. If it looks at all curdled, add a spoonful of the flour to bring it back together.
4. Sift 45 g of self-raising flour with a pinch of fine salt over the bowl and fold in with a spatula in slow figure-of-eights until no streaks remain. Loosen with 1 tsp of milk — the batter should drop reluctantly from the spatula.