Hazelnuts: Preheat oven to 350°F (176°C). Spread hazelnuts onto a rimmed baking sheet, then roast for 12 to 15 minutes, or until slightly toasted. (If your hazelnuts still have skins on them, transfer onto a kitchen towel and roll with your hands to remove skins.)
Puree Dates: Meanwhile, add dates and water to a food processor or strong blender, and puree until smooth, scraping down sides as needed. Remove date paste and wipe clean.
Puree Hazelnuts: Add roasted hazelnuts to the food processor or strong blender and run for 8 to 15 minutes, or until a smooth nut butter forms (it will go from crumbs to a thick paste to nut butter, be patient!).
Combine: Add date paste, cocoa powder, vanilla, and salt, then blitz to combine. Drizzle in almond milk, using only as much as is needed, to reach a smooth, Nutella-like consistency.
If your dates are a firm, soak them in warm water for an hour or two before pureeing.Store leftovers in the fridge for 5 to 7 dates.