Step 1: Preheat the Oven

Begin by preheating your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans. If you want easy removal later, line the bottom of the pans with parchment paper.

Step 2: Prepare the Cake Batter

In a large bowl, sift together the flour, sugar, cocoa powder, baking powder, baking soda, and salt. In a separate bowl, whisk together the eggs, buttermilk, vegetable oil, and vanilla extract. Add the wet ingredients to the dry ingredients and mix until just combined. Slowly add the hot water and stir until the batter is smooth. It will be thin, but that’s what makes the cake so moist.

Fold in the hazelnut meal for an extra layer of nutty flavor that will infuse the cake. Divide the batter evenly between the prepared cake pans.

Step 3: Bake the Cakes

Bake the cakes in the preheated oven for about 30-35 minutes or until a toothpick inserted into the center comes out clean. Once done, allow the cakes to cool in the pans for about 10 minutes, then transfer them to a wire rack to cool completely.

Step 4: Prepare the Hazelnut Filling

While the cakes are cooling, it’s time to prepare the hazelnut filling. Place the toasted hazelnuts into a food processor or blender and pulse until finely ground. You can leave a few chunks for texture if you prefer a chunkier filling.

In a saucepan, heat the heavy cream over medium heat until it starts to simmer. Remove it from the heat and whisk in the ground hazelnuts, powdered sugar, cocoa powder, vanilla extract, and a pinch of salt. Stir until the mixture thickens slightly and forms a smooth paste. Let this cool to room temperature.

Step 5: Prepare the Ganache

To make the ganache, place the chopped chocolate into a heatproof bowl. In a small saucepan, heat the heavy cream until it just begins to simmer, then pour it over the chocolate. Let it sit for 2-3 minutes, then whisk until the chocolate is completely melted and the ganache is smooth. Stir in the butter for a glossy finish. Allow the ganache to cool slightly, but don’t let it harden.

Step 6: Assemble the Cake

Once the cakes are completely cooled, use a serrated knife to level the tops if needed, ensuring they’re even. Place the first layer of cake on a serving platter or cake stand.

Spread a generous amount of the hazelnut filling over the first layer. Carefully place the second layer of cake on top, pressing gently to ensure it sticks.

Pour the chocolate ganache over the top of the cake, allowing it to drip down the sides for a beautiful, glossy effect. Use a spatula to smooth out the ganache if needed.

Step 7: Decorate and Serve

To add a finishing touch, you can decorate the cake with whole hazelnuts, chocolate shavings, or even a light dusting of powdered sugar. Allow the ganache to set before slicing and serving.