An open jar of Nutella is a dangerous thing! The only way to prevent me eating it a spoonful at a time is to cook with it, to make sure the others share it. This cake was inspired by several online, including the 'self frosting' cake here, but I've taken elements from several and made something unique, I think. If I make it again I will increase the base layer by half as much again, to make a deeper cake.
As I said earlier, my only change would be to make a deeper base cake.