Preheat the oven to 325°F and line the bottom of a 9-inch springform pan with parchment paper. Set aside

Pulse the Oreos in a blender or food processor until they become fine crumbs, then transfer them to a large bowl and mix with the melted butter.

Pour the crumb mixture into the pan and press it firmly into an even, compact layer using the bottom of a measuring cup. Bake the crust for 10 minutes, then set it aside to cool.

Place a large casserole dish or roasting pan on the bottom rack of your oven and fill it halfway with hot water. Close the oven door to keep the temperature at 325°F. This will create steam and help the cheesecake bake evenly.

In a large bowl, beat the cream cheese, granulated sugar, and brown sugar together on low speed until the mixture is completely smooth with no lumps.

Scrape down the sides of the bowl, then mix in the sour cream and vanilla on low speed until combined. Add the cornstarch, pumpkin pie spice, and salt, and mix again on low.

Add the pumpkin puree and mix on low until smooth. Add the eggs one at a time, mixing on low after each addition and scraping the bowl so everything blends evenly. Avoid mixing on high to keep excess air out of the batter.

Pour the cheesecake batter over the cooled crust. Place the pan directly above the water bath and bake for 50-60 minutes. The edges should look set, and the center should gently wobble when the pan is nudged. Keep the oven door closed during baking to prevent cracks.

Turn off the oven and prop the door open with an oven mitt. Let the cheesecake cool inside for 1 hour. After that, transfer it to the counter and let it cool to room temperature. Once fully cooled, cover the pan with plastic wrap and refrigerate for at least 6 hours or overnight so the cheesecake sets completely.

Place the chocolate chips in a heat-safe bowl. Microwave the heavy cream at 30 second intervals for 2 minutes until it’s bubbling around the edges, then pour it over the chocolate.

Let it sit for 1 minute, add the butter, and stir until the mixture is smooth and glossy. Cover the bowl and refrigerate for about 1 hour, or until the ganache thickens to a spreadable consistency.

Remove the cheesecake from the springform pan and transfer it to a serving plate or cake stand. Spread the cooled ganache over the top using an offset spatula, then garnish with flaky salt (optional). Slice and serve.