Preheat the oven to 190C/170C Fan/Gas 5 and line a 23x33cm/9x13in Swiss roll tin with baking paper. Place the eggs, sugar and vanilla seeds into a bowl and whisk until very pale, fluffy and thickened.

Line a 38x25cm/15x10in Swiss roll tin with baking parchment. In a large bowl, whisk together the eggs, sugar and half the vanilla seeds until very light, thick and fluffy. Fold in the sifted flour ...