Whisk the egg mixtures
Separate 3 eggs. Put the egg yolks, 2 tbsp sunflower oil, ½ tsp vanilla extract, 60g caster sugar, 1/8 tsp salt and the passion fruit juice in a large bowl and whisk to combine. Sift 60g plain flour, 25g white hot chocolate powder and ½ tsp baking powder into the bowl. Whisk until you have a smooth batter.
In a separate clean, non-plastic bowl, use an electric whisk to beat the egg whites until foamy and frothy. Add 1/8 tsp cream of tartar (see tip, below) and continue to whisk. Once the mix is stiffer and a little glossy, gradually add 1 tbsp caster sugar while still whisking. Continue to whisk to stiff, glossy peaks – this helps give the cakes their light texture.