Separate the eggs : Carefully separate the 5 eggs, placing the egg whites in one bowl and the yolks in another.

Whip the egg whites : Add a pinch of salt to the whites, then whisk (by hand or with an electric mixer) until they form stiff, glossy peaks.

Cream the egg yolks : In a separate bowl, whisk the yolks with the sugar and vanilla sugar until the mixture becomes pale and creamy.

Add the liquids : Gradually pour in the milk and oil while whisking gently to keep the mixture smooth.

Fold in the whipped egg whites : Add the beaten egg whites in small batches. Fold gently with a spatula to avoid deflating the mixture.

Incorporate the dry ingredients : Sift the flour and baking powder together, then fold them into the batter little by little, keeping the mixture airy.

Bake : Pour the batter into a buttered and floured cake pan.

Bake at 180°C (350°F) for 30-40 minutes, or until a toothpick inserted in the center comes out clean.