Separate the egg whites from the yolks. Add a pinch of salt to the egg whites and beat until stiff peaks form. Add the sugar and vanilla sugar to the yolks and beat with an electric mixer until the mixture doubles in size.

Gently fold the yolk mixture into the egg whites. Gradually sift in the flour, folding gently to keep the batter light and airy.

Spread the batter onto a baking sheet lined with parchment paper. Bake at 350°F (180°C) for 15 minutes, using both top and bottom heat if possible. While still hot, roll the cake up from the shorter side with the parchment paper. Then wrap it in a damp kitchen towel and let it cool.

Whip the heavy cream with the vanilla sugar until stiff peaks form, then set aside. Chop the Kinder ingredients and gently fold them into the whipped cream.

Melt the semisweet chocolate and pour it along the center top of the roll, letting it spread naturally. Melt the white chocolate and drizzle it in thin lines for decoration. Finish decorating with Kinder Happy Hippo treats and pieces of Kinder Bueno.