Spray a 9x9 baking dish with nonstick cooking spray. Line with parchment paper.
In a bowl, stir together graham crackers and butter until all the crumbs are wet. Press into the bottom of the prepared baking dish.
Pour cold water into a small bowl. Sprinkle gelatin over water and allow to bloom for 5 minutes.
Meanwhile, pour heavy cream into a large mixing bowl. Whip until stiff peaks form. Set aside.
In a separate large mixing bowl cream together cream cheese and powdered sugar until light and fluffy, about 2-3 minutes. Whip in sour cream and vanilla extract.
Microwave gelatin mixture for about 15 seconds, or until it turns clear. Pour into cream cheese mixture while mixing. Fold whipping cream in with the cream cheese until well combined. Spread on top of graham cracker layer.
Place Nutella into a small bowl. Microwave for 30 seconds to thin it out. Drizzle it over the cream cheese layer. Use a butter knife to gently swirl it around.