Preheat Your Oven: Start by preheating your oven to 180 degrees Celsius (top/bottom heat).

Cream the Butter and Sugars: In a mixing bowl, beat the soft butter with the white sugar, brown sugar, and a splash of vanilla extract until the mixture is light and creamy.

Incorporate the Eggs: Add the eggs one at a time, beating well after each addition until the mixture becomes foamy.

Mix Dry Ingredients: In a separate bowl, whisk together the flour and baking powder, then gradually stir this into the creamed mixture.

Fold In the Nuts and Chocolate: Carefully fold in the ground hazelnuts, chopped hazelnuts, and grated chocolate. Lastly, add the yogurt and mix until well combined.

Prepare Baking Pan: Butter and flour a 26 cm baking pan, then pour the batter into the prepared pan.

Bake: Place in the oven and bake for approximately 50 to 60 minutes, checking for doneness using the classic chopstick test.

Cool and Fill: Allow the cake to cool before slicing it horizontally in the middle. Spread raspberry jam on the bottom layer and place the top layer back on.

Apply Marzipan and Chocolate: Cover the top with a marzipan layer, then melt the couverture chocolate and spread it over the marzipan.

Decorate: Feel free to finish with any additional decorations or toppings you like!