Preheat oven to 350°F (180°C). Line the bottom of a 9.5–10-inch (24–25 cm) springform pan with parchment paper and lightly grease the sides with sunflower oil.

In a large mixing bowl, beat the eggs with the sugar, vanilla sugar, and a pinch of salt using a stand or hand mixer on high speed until the mixture becomes pale, airy, and triples in volume.

Sift the flour and baking powder into the egg mixture in batches, gently folding with a silicone spatula after each addition to preserve volume.

Pour the batter into the prepared pan, smooth the surface, and bake for 35 minutes, or until golden and a toothpick inserted in the center comes out clean.

Let the cake cool completely in the pan at room temperature before slicing.

In a medium bowl, whip the mascarpone with sugar and vanilla extract until creamy. If too thick, add a little cold heavy cream until smooth and spreadable.

Slice the cooled sponge cake horizontally into two even layers.

Place the first layer on a serving plate or cake stand. Spread half the mascarpone cream over it and arrange half the sliced strawberries on top.

Add the second sponge layer and repeat with the remaining cream and strawberries.

Decorate with additional strawberries and fresh mint if desired.

Chill the cake in the fridge for at least 1 hour before slicing to help it set.