Sponge cake

Method

1. Preheat the oven to 180°C and butter and lightly flour a 26 cm cake tin.
2. To make the sponge, first combine the sifted flours in a bowl.
3. In another mixing bowl, whisk the eggs whites to soft peaks, then gradually add the sugar and continue whisking to form a glossy meringue. Leave the motor on a medium speed and add the yolks one by one, mixing until combined. Gently fold in the combined flours.
4. Pour the batter into the prepared tin and bake for 35 minutes. Remove from the oven and leave to cool.
5. To make the custard, put the milk into a large saucepan with half the caster sugar and the vanilla bean and bring to the boil.
6. Meanwhile, whisk together the egg yolks and the remaining sugar, then add the cornflour to form a paste. Carefully pour a little hot milk onto the yolk paste, whisking well to incorporate. Continue slowly adding the hot milk until half is used. Remove the vanilla bean, split it and scrape the seeds into the remaining milk. Bring the milk back to the boil and pour it onto the yolk mixture. Tip the whole lot back into the saucepan over a medium heat. At this point the custard will thicken quickly, so work fast and continue whisking until it returns to the boil. Cook for a few minutes to make sure the flour has lost its raw taste, then pour the custard into a clean bowl and cover the surface with clingfilm.
7. Refrigerate until it has cooled completely. When you are ready to fill the sponge, beat the custard briefly using an electric beater to ensure it is really smooth.
8. When the cake is completely cool, split in half and fill with lavish amounts of custard.