Lightly grease 9x9-inch baking pan with nonstick cooking spray, then line the pan with parchment paper.
In a small mixing bowl, stir 1 cup crushed graham cracker crumbs together with 5 tablespoons melted butter until all the crumbs are wet. Press into the bottom of the prepared baking dish.
Pour 2 tablespoons cold water into a small microwave-safe bowl. Sprinkle 1 1/2 teaspoons unflavored gelatin over the water and allow to sit and bloom for 5 minutes.
Meanwhile, pour 2/3 cup heavy cream into a large mixing bowl. Use a hand mixer to whip until stiff peaks form. Set aside.
In a separate large mixing bowl use a hand mixer to cream together 16 ounces cream cheese and 3/4 cup powdered sugar until light and fluffy, about 2-3 minutes. Whip in 1/4 cup sour cream and 1 1/2 teaspoons vanilla extract.
Microwave gelatin mixture for about 15 seconds, until it turns clear. Pour directly into the cream cheese mixture while mixing. Use a rubber spatula to fold the whipped cream in with the cream cheese until well combined. Spread this on top of the graham cracker crust.
Place 1/3 cup Nutella into a small microwave-safe 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.
Refrigerate, uncovered, for 4 hours until set. Slice and serve when ready.