One cannot say this is low in calories or a daily treat, but if you're gonna bake something that “extreme”, at least choose the healthiest ingredients you can find.
I made this with organic eggs, of course. Then bought some delicious organic nut nougat butter, which tastes exactly the same (or even better) without the creepy ingredients of the real Nutella. That's it.
The secret here is to fold eggs very slowly into batches, as described on the link below.
From Kirbi’s CreavingsRecipe: http://kirbiecravings.com/2012/03/2-ingredient-flourless-nutella-cake.html