Toast the Hazelnuts: Preheat your oven to 350°F (175°C). Spread the hazelnuts in a single layer on a baking sheet. Roast for 10-12 minutes until they are golden brown and fragrant. Keep an eye on them to prevent burning.
Remove the Skins: Let the hazelnuts cool slightly. To remove the skins, wrap them in a clean kitchen towel and rub vigorously. It's okay if a few bits of skin remain.
Make the Nut Butter: Transfer the toasted hazelnuts to a food processor. Blend for 5-8 minutes until you get a smooth and creamy nut butter, scraping down the sides as needed.
Melt the Chocolate: While the nuts are blending, melt the chocolate. You can do this in a microwave-safe bowl in 20-second intervals, stirring in between, or use a double boiler on the stovetop.
Combine the Ingredients: Add the melted chocolate, cocoa powder, condensed milk (or maple syrup), vegetable oil, vanilla extract, and a pinch of salt to the food processor. Process until smooth and creamy.
Adjust the Consistency: If the spread is too thick, you can add a little more oil (1 tsp at a time) until you reach your desired texture.
Store: Transfer the homemade Nutella to a clean jar. Store at room temperature for up to 2 weeks or refrigerate for longer shelf life. Note that refrigeration may make it firmer; let it come to room temperature before spreading.