Preheat the oven to 180°C / 350°F and line the baking tray with parchment paper.

Whisk the 2 eggs with 120 g granulated sugar and the vanilla sugar until the mixture is pale and slightly foamy.

Whisk 150 ml neutral vegetable oil into the egg mixture until smooth.

Add 300 g wheat flour, 50 g cornstarch, and the baking powder to the bowl.

Fold the dry ingredients into the wet mixture with a rubber spatula until a soft, non-sticky dough forms.

Divide the dough into 12 equal portions and flatten each portion into a small disc.

Place about 16 g Nutella hazelnut cocoa spread in the center of each dough disc and seal the dough around the filling.

Roll each filled portion into a smooth ball and arrange the balls spaced apart on the lined baking tray.

Bake the Nutella balls at 180°C / 350°F for 12 to 15 minutes until set but still pale.

Cool the Nutella balls on the baking tray for 5 minutes, then transfer them to a wire rack to cool completely.