Whisk eggs with sugar until they are three times in volume, light and fluffy.
Sift flour, cocoa and baking powder. Mix in with ground nuts.
Using spatula, fold in dry ingredients by thirds, be very gentle with the dough so you don’t over mix it and loose the fluffiness. Butter all sides of the 9 inch baking dish, pour batter into the dish.
Bake at 350F for about 40 minutes.
Cream
Prepare ingredients for the cream.
Dissolve chocolate, either in water bath or microwave. Let chocolate cool to a room temperature. Combine chocolate together with butter and Nutella. Whisk cream together.
Assembly
Slice the cake into two or three layers. Break wafers into small pieces. Spread cream over each layer evenly, sprinkle wafers over the cream
Decorate outside of the cake, using the left over cream, cake and hazelnuts. Slice ferrero rochRr candy in half and place it on the edge of the cake all around.
Just before serving the cake, remove from refrigerator to soften the cream a little.