I found this recipe on let the baking begin but I think originally it was posted on this site. Such a fantastic recipe and must try cake. 

Ingredients:
For the Cake
7 large eggs at room temperature (leave out for half hour)
1/2 cup sugar
2 cups finely ground hazelnuts (I ground whole hazelnuts with a food processor)
3 Tbsp all purpose flour
3 Tbsp cocoa powder
3 tsp baking powder

For the Frosting
1 cup and 4 tablespoons unsalted butter, room temperature
2 1/4 cups semi-sweet chocolate chips
1/2 cup Nutella
Ferrero Rocher for the top
3/4 cups hazelnuts, chopped

Instructions:

Preheat oven to 350 F.

Spray two 8 inch round pans with non stick spray, or butter the sides and set aside.

Sift flour, cocoa & baking powder. Stir in ground nuts (see consistency of ground nuts below). This will give your cake a wonderful crunchy texture. 

Whip eggs on high speed, until frothy. Slowly add the sugar and continue whipping until tripled in volume (approximately 5 minutes).

Fold dry ingredients into the eggs , in 2 additions. Divide the batter evenly between two baking pans and bake until a toothpick inserted in the center comes out clean (approximately 15-20 minutes).

Once baked, leave in the pan for 5 minutes, then transfer to a cooling rack.

In the meantime, begin the frosting by melting the chocolate chips in microwave,in 30 second intervals, stirring between each time. Bring to room temperature and then whip chocolate, butter and Nutella until thoroughly combined and set aside.

Crush wafers by putting in a ziplock bag, then going over them with a rolling pin or something heavy.

To Assemble the Cake:

Once the cake has cooled, split each cake in two even layers (my cake didn't rise properly that is why it looks shorter in the pictures, and that is why I did not cut each layer into two layers).Reserve some frosting for decorating. Place a dab of frosting onto a serving platter or cake board, to hold it in place. Put 1 cake layer on top and press to adhere.

Put 1/4 of the remaining frosting onto the cake and spread around evenly. Sprinkle with 1/3 of the crushed wafers.Repeat above 2 steps with the remaining cake layers. Once all your layers are complete frost the top and sides of the cake with the reserved frosting.

Using your hands, press the chopped hazelnuts into the frosting around the sides of your cake.

Pipe 8 stars on top of the cake and place one Ferrero Rocher candy on top of each piped star. If you are not eating it right away store in the refrigerator and bring to room temperature before you're about to enjoy :)