• Line the bottom of an 8 or 9-inch springform pan with parchment paper. Lightly spray the sides of the pan with non-stick spray. Wrap the pan with at least 4 layers of heavy-duty aluminum foil, and then tie an oven liner around the pan to prevent water seeping in from the water bath. If you don't have an oven liner, make sure the pan is wrapped very well with extra layers of foil.
• Preheat your oven to 325°F and start boiling water for the water bath.

Make the Oreo Crust:

• Add the Oreo cookies to a food processor and pulse into fine crumbs. Add the melted butter and mix until evenly combined.
• Pour the crust mixture into the prepared springform pan. Spread it out evenly, then use the flat side of a glass or measuring cup to pack it down tightly into the bottom and slightly up the sides of the pan.
• Prebake the crust for 10 minutes while you make the filling.

Make the Cheesecake Filling:

• Use an electric mixer to beat the softened cream cheese until smooth. Wipe any lumps of cream cheese off of the mixer and the sides of the bowl, then add the granulated sugar, sifted cocoa powder, salt, and cornstarch, and mix until evenly combined.
• Wipe the sides of the bowl, then add the room temperature sour cream, vanilla extract, and red gel coloring. Add more color if needed, and mix to combine. Make sure the cheesecake batter is completely smooth with no lumps at this point, because you want to mix as little as possible once the eggs are added.
• Add the room temperature eggs, one at a time, and mix on low speed until just combined after each. Wipe the sides of the bowl with a rubber spatula and mix until the batter is smooth.
• Pour the batter into the springform pan over the pre-baked crust. Bang the pan on your counter a few times to release any pockets of air.

Bake:

• Set a large roasting pan on the bottom rack in your oven. Pour the boiling water into the roasting pan, about an inch high inside of the roasting pan. Carefully set the springform pan inside the roasting pan.
• Bake the cheesecake for 60-80 minutes, until set around the edges and only slightly wobbly in the center.
• Turn the oven off, crack open the door, and leave the cheesecake inside for 1 hour to slowly come to room temperature. Remove the cheesecake from the oven and the water bath and let it cool completely at room temperature for at least 1 hour. Then refrigerate overnight, still in the springform pan.
• When ready to serve, remove the sides of the springform pan and use a large, sharp knife to slice the cheesecake. Run the knife under hot water and wipe it clean between each slice.
• Cover leftovers and keep in the fridge for up to 3 days. You can also freeze the cheesecake for up to 3 months. Thaw in the fridge when ready to serve.