Beat the eggs, sugar and vanilla sugar until light and fluffy. I beat this in a stand mixer on medium-high speed for about 10 minutes.

Sift the flour and cornstarch and add to the mixture. Fold this gently into the mixture; you don't want all the air you whipped in to disappear.

Pour the batter into a greased baking pan. Bake the cake base at 180°C/350°F (conventional oven) for 30 minutes. The cake is done when you press lightly on the top and it springs back. Allow the cake to cool in the pan for a few minutes before removing it to a cake rack.

Meanwhile, prepare the nougatine and jam according to the recipe if you haven't already.

Let the cake cool completely before you cut it. If, like me, you used a 20 cm/8 inch spring form pan, cut the cake into three layers.

Whip the cream and sugar until you have stiff peaks.

Place the bottom layer of sponge cake on a cake stand or plate and spread half the jam on top, leaving about ½ inch of jam around the edges. Place a few tablespoons of whipped cream on top of the jam and spread evenly. Place the second layer of sponge on top and fill in the same way. Finish with the last layer of cake.

Spread the sides of the cake with the whipped cream (it does not have to be thick) until it is completely covered, but leave enough whipped cream for the swirls.

Cover the sides of the cake with the caramelized hazelnut pieces. To do this, take a handful of hazelnut crunch at a time and press it against the side of the cake. Continue until the entire side is covered with nougatine.

Place the remaining whipped cream in a piping bag with a star tip and pipe swirls on top of the cake around the edge. Place a piece of fruit of your choice in each swirl. I used kiwi, strawberry, and blueberry.