Sponge Fingers

• 5 egg yolks
• 125 g (4½ oz) golden caster sugar

Preheat the oven to 150°C (300°F, Gas Mark 2).

Whisk the egg yolks with two-thirds of the sugar until the yolks are thick, pale and much increased in volume.

In a separate bowl, whisk the egg whites, slowly adding half the remaining sugar, until the mixture forms stiff