OK I did some reading on Nutella.
Invented in Italy during WW2 when there was a chocolate shortage, in an area of Italy where hazelnuts are grown.
Originally a substitute for hard chocolate it was reformatted into a spread in the late 50s. The main ingredient is SUGAR. Second ingredient by percentage is Palm Oil.
Sugar and Palm oil makes up 70 percent of the spread. Add to that the roasted ground hazelnuts and whey solids, soy lethicin,cocoa powder and vanillin. There you have Nutella. Factories are making it in Italy, Australia, and Canada.
Making it from a powder would require carrying a lot of palm oil, since you could not just add water, although some water would be needed.
The fat in Nutella is almost all saturated fat, BTW.
This, in my opinion, makes it a poor calorie source, trail or not.
A similar trail food might be possible with powdered milk, cocoa mix, sugar, and vanilla, mixed with roasted hazelnut flour and water. Without the oil it would simply not taste the same as Nutella.
Bobs Red Mill sells only blanched hazelnut flour, not the roasted type. But there are sources for roasted flour, I discovered via google.