Sponge Biscuit

Ingredients

• 6 eggs
• 250 g icing sugar
• 100 g wheat flour
• 50 g potato flour (starch)
• 30 g butter
• lemon zest

Instructions

1. Work the yolks with the sugar and a little flour at least half an hour.
2. Fold in the stiffly whipped whites, then sift in the two dried flours.
3. Bake in a greased, dusted tray about three fingers tall.