Have you tried buying the individual nutellas? They are basically only one sandwich worth at a time. They come in little rows and you just use one serve at a time (unless you are pregnant that is...).

DS has a very high calorie diet (medical condition requires it) and so I have chocolate and chips in the cupboard all the time . My Nutella eating was really a bit silly until I found the individual serves. That helped me be a bit more honest with myself about how much I was eating of the stuff. Snack amnesia is a bit of a problem for me .

Good luck!