Begin by heating the oven to 350°F. Prepare a 9-inch springform pan by lining the bottom with parchment paper and lightly coating the pan with nonstick spray so the crust releases easily later.

Place the Oreo cookies in a food processor or blender and pulse them until they turn into fine crumbs. Measure out about 1½ cups of these crumbs and transfer them to a bowl. Stir in the granulated sugar so it is evenly distributed.

Pour in the melted butter and mix everything together until the crumbs resemble damp sand and hold together when pressed.

Tip the crumb mixture into the prepared pan and press it firmly across the bottom and partway up the sides, creating an even crust.

Bake the crust for about 10 minutes. Once baked, remove it from the oven and allow it to cool slightly. When it has cooled a bit, wrap the outside of the pan completely with aluminum foil, covering the bottom and sides to prepare it for the water bath later.

Place the chopped chocolate in a microwave-safe bowl. Heat it in short 20-second bursts, stirring well after each interval, until it melts completely and becomes smooth. Set it aside to cool slightly.

In a stand mixer fitted with the paddle attachment, or in a large mixing bowl with electric beaters, beat the cream cheese for a few minutes until it becomes smooth and creamy. Pause to scrape down the sides and bottom of the bowl so everything blends evenly.

Add the granulated sugar and continue mixing for about 2 to 3 minutes until the mixture is silky.

Blend in the sour cream and vanilla extract, mixing only until everything is combined.

Add the eggs one at a time, mixing gently after each addition just until incorporated. Use a rubber spatula to scrape the bowl so no pockets of batter remain unmixed.

Scoop about 2 cups of the plain cheesecake batter into a separate bowl. Stir the melted chocolate into this portion, making sure the chocolate is still fluid but no longer warm. This will become the chocolate cheesecake mixture.

Drop spoonfuls of the vanilla batter and the chocolate batter into the crust, alternating between the two. Since there is more vanilla batter, make those scoops a bit larger, or add two scoops of vanilla for every scoop of chocolate.

Once all the batter is in the pan, take a butter knife and gently swirl the two mixtures together to create a soft marbled pattern.

Lightly tap the pan on the counter a few times to release any trapped air bubbles, then smooth the top.

Set the springform pan inside a 10-inch cake pan, then place that into a large roasting pan. Pour hot water into the roasting pan until it reaches about 1 inch up the sides, forming a water bath.

Bake in the preheated oven for 60 to 80 minutes. The cheesecake is ready when the edges are set while the center still has a slight wobble.

Turn off the oven and leave the door slightly open. Let the cheesecake rest in the warm oven for about 1 hour.

After that, remove it from the oven and allow it to cool at room temperature for roughly 2 hours.

Cover the cheesecake and refrigerate it for at least 6 hours, though chilling it overnight gives the best texture.

When ready to serve, run a thin knife around the edge of the pan to loosen the cheesecake, then gently release the springform ring. Slice and serve with whipped cream, fresh fruit, chocolate sauce, or any topping you like.