• Line the bottom of an 8-inch springform pan with parchment paper. Lightly spray the sides of the pan with nonstick spray.
• Wrap the pan with several layers of heavy duty aluminum foil, then tie a slow-cooker oven liner around it (recommended) to keep water leaking into the pan from the water bath.
• Arrange your oven rack to the lower position. Preheat your oven to 325°F and start boiling water for the water bath.

Make the Oreo Coffee Crust:

• Add the Oreo cookies to a food processor and grind into fine crumbs. Mix in the instant espresso powder and salt to combine. Then add the melted butter and pulse until the mixture is well combined.
• Press the crust tightly and evenly into the bottom and slightly up the sides of the prepared springform pan. Place the pan on a large baking sheet and prebake the crust for 10 minutes while you make the filling.

Coffee Cheesecake Filling:

• In a large bowl, use an electric mixer to beat the softened cream cheese until smooth with no lumps. Wipe any lumps off of the mixer and sides of the bowl. Add the granulated sugar and cornstarch and mix until well combined.
• Mix in the room temperature sour cream, vanilla extract, instant espresso powder, cocoa powder, and salt. Wipe the sides of the bowl with a rubber spatula. Make sure the filling is completely smooth and there aren't any lumps at this point.
• Switch to a whisk and mix in the room temperature eggs, one at a time, until just combined after each. Don't overmix.
• Pour the cheesecake batter into the pan over the prebaked crust. Bang the pan on your counter several times to get rid of any trapped air bubbles.

Bake:

• Place a large roasting pan on the rack in your oven. Add about an inch of boiling water to the pan, then gently place the cheesecake inside the pan.
• Bake the cheesecake for 1 hour without opening the oven door to check on it. After 1 hour, check if the cheesecake is done by gently shaking the pan. If it looks set around the edges with a slightly wobbly center, then it's done. If it's still really wobbly all over, keep baking and check again in 5-minute intervals. Mine needed 1 hour + 10 minutes total, but the time can vary. When in doubt, it's better to slightly under-bake the cheesecake than it is to over-bake it.
• Once the cheesecake is set around the edges with a slightly wobbly center, turn your oven off and crack the door. It will continue to bake and set as it cools. Leave the cheesecake in the oven for at least 1 hour to slowly cool to room temperature.
• Remove the cheesecake from the oven and the water bath and let it cool completely at room temperature. At least another hour, it shouldn't feel warm at all when you put it in the fridge.
• Once the cheesecake is completely cooled to room temperature, refrigerate it (still in the springform pan) overnight to set the filling.

Coffee Chocolate Ganache:

• Add the chopped chocolate or chocolate chips and heavy cream to a glass measuring cup. Microwave in 30-second intervals, stirring between, until melted. Stir in the instant espresso powder and spread the ganache over the top of the cooled cheesecake.
• When ready to serve, use a large, sharp knife to slice the cheesecake. Wipe the knife clean between each slice.