Take 3 bowls to separate the whites from the egg yolks. In 2 of the bowls, place 6 egg whites in each, and all 12 yolks together in the third bowl.

Cover the bowls with cling film, return the yolks to the refrigerator.

Let the egg whites sit on the kitchen table, at room temperature, for 12-24 hours.

Meanwhile, put the hazelnuts in a tray and toast them in the oven, stirring periodically. They can burn very quickly, so be careful.

After they cool down, grind them coarsely in a food processor, or chop with a knife.

In 2 plates (one for each layer of cake) combine together:

- 200g of sugar;

- 50g of flour;

- 175g of hazelnuts.

Line with baking paper the base and the sides of a 28cm diameter springform pan.

Grease the paper with a little oil or soft butter. For even more stickiness, you can also grease the sides of the pan with a bit of oil, before lining.

In a large bowl, put the first 6 egg whites and beat to soft peaks. Then, gradually add 50g of sugar and continue to whisk until stiff peaks form.

Add the contents of the first plate: 200g of sugar, 50g of flour and 175g of chopped hazelnuts, plus 1 sachet of vanilla sugar.

Carefully mix with a spoon or spatula.

Move this mixture to the pan lined with baking paper, level out.

This will be the first cake layer.

Place in the preheated oven to 140 degrees C for 2.5 hours. We want to dry it well, without browning too hard, see the picture.

After the oven, remove from the pan and leave it on a wire rack to cool, up side down.

Then we prepare the second cake layer. Repeat steps 6-10: line the pan again with baking paper, beat 6 egg whites with 50g of sugar and mix in the 200g of sugar, 50g of flour and 175g of roasted hazelnuts (the second plate).

Bake in the same way for 2.5 hours at 140 degrees C.

You'll notice both the layers are well dried only at the top, while the base is a little wet. In order to dry completely, let the cakes dry base up on a grill at room temperature for 24 hours.

On the day you assemble the cake, in the morning you must make the egg yolk syrup from the egg yolks left in the refrigerator, as follows:

Bring to the boil 350ml of milk mixed with 300g of sugar in a saucepan, then leave it on the table for 15-20 minutes to cool.

Beat the egg yolks well with a whisk or mixer, then gradually add in the boiled milk.

Pour this mixture back into the saucepan and place over heat. Stirring continuously, cook until it starts to boil and thickens slightly.

Let this syrup cool at room temperature for 5-6 hours, covered with cling wrap.

In the meantime, don't forget to take 400g of butter out of the fridge.

After this time, we'll start to assemble the cake, but first we must prepare the filling.

In a large bowl, beat well with the mixer 400g of butter, then gradually add the yolk cream until you have a smooth mixture.

Place one cake on a plate and spread over with a thin layer of buttercream, about a third of the whole amount.

Cover with the other cake layer. I placed the layers bottom up, so that the cake is smoother at the top.

Add 2 spoons of cocoa to the remaining filling, mix.

You can fill a piping bag with 2-3 spoons of white cream to decorate the top with it.

Spread the cocoa cream on the cake, on the sides and on top.

Smooth out with a knife. Optionally, you can decorate it with some white buttercream.

Or you can simply sprinkle the top with the remaining 50g of toasted hazelnuts.

Keep the cake in the fridge for about 8-10 hours before serving.

Here is a section. The portions must be small as this is a very filling cake, and yet so special and tasty.

Enjoy!