Prepare the Crust:

1. Preheat oven to 325°F (163°C). Grease an 8×8-inch baking pan with butter or line it with parchment paper; set aside.
2. In a food processor, pulse graham crackers into fine crumbs.
3. Add melted butter and pulse until fully combined.
4. Pour the mixture into the lined baking pan and press down evenly using your hands or the bottom of a measuring cup.
5. Bake for 5 minutes, then remove from the oven.

Make the Cheesecake Filling:

1. While the crust is baking, beat cream cheese and sugar in a stand mixer (or by hand) for 2 minutes, until light and fluffy.
2. Add eggs one at a time, beating between each addition.
3. Mix in vanilla extract and beat until smooth and lump-free.
4. Pour the cheesecake mixture over the pre-baked crust and smooth into an even layer.

Add the Nutella Swirl:

1. Drop large spoonfuls of warmed Nutella over the cheesecake filling.
2. Use a knife to gently swirl Nutella into the batter, creating a marbled effect.

Bake & Chill:

1. Bake for 30 minutes, or until the center slightly jiggles but is mostly set.
2. Remove from oven and let cool completely.
3. Refrigerate for at least 3 hours, or freeze for 1 hour for faster setting.
4. Once chilled, remove from the pan using the parchment paper and slice into 9 bars.