Preheat the Oven: Begin by preheating your oven to 180 degrees Celsius (or 160 degrees for a fan oven). This sets the stage for a perfectly baked cake.

Prepare the Egg Mixture: Separate the egg whites and yolks. Beat the egg whites until stiff peaks form, and set them aside. In another mixing bowl, combine the egg yolks with the sugar and vanilla sugar, whisking until foamy.

Combine Ingredients: Gradually add breadcrumbs, grated dark chocolate, and ground hazelnuts to the egg yolk mixture, mixing well. Then, fold in cocoa powder and baking powder.

Fold in Egg Whites: Gently incorporate the beaten egg whites into the mixture, being careful not to deflate them. This will ensure your cake layers are light and airy.

Bake the Layers: Line a springform pan (Ø 26 cm) with baking paper and pour in the cake batter. Bake for approximately 25-30 minutes, or until a toothpick inserted in the center comes out clean. Allow the cake to cool completely before slicing it horizontally into three layers.

Prepare the Cream: While the cake cools, mix the whipped cream with the cream stiffener using a hand mixer and refrigerate. Meanwhile, soak the gelatin in cold water.

Make the Mascarpone Cream: Combine mascarpone, sugar, and coffee cream liqueur in a bowl. Mix instant coffee powder with 2 tablespoons of hot water, and stir this into the mascarpone mixture.

Incorporate Gelatin: Squeeze out the softened gelatin and dissolve it in a small saucepan. Once dissolved, add a bit of the mascarpone mixture to the gelatin, stirring well before combining it back into the main cream mixture.

Assemble the Cake: Begin layering the cake by placing one layer on a serving platter. Spread a portion of the mascarpone cream on top, then repeat the process with the other layers. Finish with a thick layer of cream on top.

Decorate: For an extra touch, garnish with dark chocolate shavings, or berries. Refrigerate the cake for a few hours or overnight to set the flavors.