Preheat the oven to 340F(170C).

Mix the hazelnuts with flour and salt.

In a standing mixer fitted with a whisk attachment, beat the egg whites on low to medium-low speed until foaming, taking about 1 minute. Keep beating until the egg whites increase approximately four times in volume. Add the sugar and the lemon juice.

Increase the mixer's speed to high and continue beating the egg whites to a stiff peak stage.

Stop the mixer and add the flour, salt, and hazelnuts with a spatula, mixing gently from underneath to the surface, carefully not losing the air from the egg whites.

Strawberries, water, lemon juice, sugar, and corn starch go in a medium pot on the stove on medium heat.

In a small pan, toast the pistachios until they develop the flavor, and add them to the strawberry compote.

Place the springform pan in the freezer.

Place the gelatin sheets in a pan with icy water to cover them and let the gelatin sheets hydrate. The gelatin is hydrated and ready to use when it is very soft. Squeeze the gelatin in your hands to get rid of the water, then place it over the white chocolate.

Meanwhile, bring the milk to a boil. Remove it from the stove and pour it over the gelatin and white chocolate.

Let it sit for about 2 minutes, then gently mix it. Let the mixture cool.

While the chocolate cools down, whip the heavy cream to a medium soft peak and fold it gently into the cool white chocolate mixture.

Place the gelatin sheets in a pan with icy water to cover and let the gelatin sheets hydrate. The gelatin is hydrated and ready to use when it is very soft. Squeeze the gelatin in your hand to get rid of the water, then place it over the white chocolate.

Bring the heavy cream to a boil and pour it over the chocolate and gelatin. Add the butter and mix slowly just on the bottom of the bowl, right in the center, in small circles. The idea is to obtain a smooth, shiny glaze that doesn't have air bubbles when poured on the cake. Let it cool, then glaze the cake with it.

Remove the parchment paper from the bottom of the 8 inches cake. Place the cake back in the springform pan.

Add about ⅓ of the white chocolate mousse over the cake.

Remove the 6 inches pan from the freezer and remove the strawberry and cake insertion. Remove the parchment paper from the bottom of the cake.

Place the 6 inches cake and strawberry insertion(which should be hard frozen) in the middle of the 8 inches cake over the chocolate mousse.

Pour the rest of the white chocolate mousse over and level the surface with a spatula.

Place the cake in the freezer for 24 hours.

The next day, place the cake on a metal rack. Place a tray underneath the rack.

Pour the glaze over the cake. Grab the cake from underneath with a wide spatula and place it on a serving platter. Refrigerate so the glaze hardens.

Decorate it with fresh berries, white chocolate, and a few golden sprinkles.

This cake needs refrigeration. After decoration, the cake must stay in the fridge to defrost for 2 hours before serving it.