Preheat oven to 350 degrees. Butter bottom and sides of a 9-inch springform pan.
Sift flour, cocoa and baking powder. Mix with ground nuts.
Beat eggs with sugar until they are light and fluffy and triple in volume.
Gently fold dry ingredients by thirds into wet. Don't over mix. Pour into prepared pan and bake for 40 minutes. Allow to cool completely in pan before removing sides.
For the Nutella buttercream...
Melt the chocolate in the microwave, then allow to cool to room temperature. Beat chocolate with butter and Nutella.
To assemble...
Using a long sharp knife, slice cake into two layers. Spread buttercream and crushed wafers between layers. Frost edges and top of cake with remaining buttercream.
Press chopped hazelnuts onto sides of cake. Cut Ferrero Rocher candies in half and place around the edge of cake. Chill.
Before serving remove from the refrigerator to allow the buttercream to soften.
Notes
This recipe is not affiliated with the Ferrero Company.