Preheat your oven to 325°F (165°C) and line an 8x8-inch baking pan with parchment paper for easy removal.

In a mixing bowl, combine chocolate sandwich cookie crumbs and melted salted butter until well mixed. Press this mixture firmly into the bottom of the prepared pan to form an even layer.

Bake for 8 minutes, then let it cool completely on a wire rack.

While the crust cools, prepare a water bath for baking your Nutella cheesecake bars by filling a rimmed baking dish with about 1 inch of water and place it on the bottom rack of the oven.

In a large mixing bowl, beat the softened cream cheese with an electric mixer on medium speed until smooth and creamy, about 2 minutes.

Gradually add granulated sugar, mixing until combined. Then, blend in full-fat sour cream and vanilla extract.

With the mixer on low, add eggs one at a time, incorporating each until the mixture is smooth and creamy throughout.

Once your filling is smooth, separate half of the cheesecake mixture into another bowl. Add Nutella to one half and blend until fully incorporated. In the other half, gently fold in crushed Oreo crumbs.

Pour alternating layers of the Oreo-infused cheesecake batter and the Nutella cheesecake batter into the prepared crust, creating a marbled effect. Swirl warm Nutella on top using a knife.

Place the assembled Nutella cheesecake bars in the oven with the water bath still in place. Bake for 55-65 minutes.

When done, gently shake the pan; the center should have a slight jiggle. Remove from the oven and let it cool completely at room temperature.

Transfer to the refrigerator and chill for at least 2 hours before slicing into bars.