Unfortunately, we do not have safe canning instructions for a product like Nutella. It is a thick, very low acid product and would require long, intense heat to make it shelf-stable. That heating would most likely destroy the quality of the product. Cocoa and nuts make products challenging to preserve. Have you tried freezing it? There would be no safety concerns in freezing and it should maintain it's texture. Try a small container first, before freezing a large batch.