Preheat oven to 180 degrees C (350 degrees F). Line a 1,5 l heart shaped pan with a sheet of baking paper and grease well on top (if your pan is made of silicone, the paper is not necessary).
In a bowl combine starch, cocoa powder and baking powder and stir.
In a large bowl using an electric mixer beat sugar with 3 yolks and 1 white for 5-6 minutes, until thick and creamy. Add olive oil and vanilla and beat shortly again.
Wash and wipe the beaters of the mixer and beat separately the last egg white in another bowl until thick foam.
Using a rubber spatula gradually fold the dry ingredients into the eggs and sugar mixture. At the end fold in also the egg yolk.
Pour the batter into the prepared pan. Bake for 30-35 minutes or until a toothpick inserted in the centre comes out clean. Let the cake cool until room temperature, then wrap it in cling film and transfer to the fridge for at least 2 hours.