1. Preheat the oven to 325°F (160°C). Line the bottom of a 9 inch springform pan with parchment paper and lightly grease the sides.

2. In a bowl combine the chocolate cookie crumbs, granulated sugar, and melted butter until the mixture feels like damp sand.

3. Press the crumb mixture firmly into the bottom of the prepared pan and bake for 10 minutes. Set aside to cool slightly while you prepare the chocolate cheesecake layer.

4. For the chocolate cheesecake layer beat 16 ounces softened cream cheese with 3/4 cup granulated sugar until smooth and fluffy.

5. Add the cocoa powder and cornstarch and mix until no dry streaks remain scraping down the bowl as needed.

6. Beat in 2 large eggs one at a time followed by 1 teaspoon vanilla extract and the sour cream until the batter is thick glossy and completely smooth.

7. Pour the chocolate cheesecake batter over the baked crust and smooth the top with a spatula.

8. Bake for 25 to 30 minutes until the edges are set and the center still has a gentle wobble. Let the pan cool on a rack for 10 to 15 minutes.

9. Spoon the cherry pie filling or drained cherries evenly over the warm chocolate cheesecake layer going all the way to the edges.

10. For the vanilla cheesecake layer beat 16 ounces softened cream cheese with 1/2 cup granulated sugar until creamy and smooth.

11. Add the cornstarch and mix well then beat in 2 large eggs one at a time followed by 1 teaspoon vanilla extract and 1/2 cup heavy cream.

12. Gently pour the vanilla cheesecake batter over the cherry layer using the back of a spoon or spatula to help it spread without disturbing the cherries too much.

13. Return the pan to the oven and bake for 35 to 40 minutes or until the edges are set and the center still jiggles slightly when the pan is gently shaken.

14. Turn off the oven crack the door open and let the cheesecake sit inside for 30 minutes to cool slowly and reduce cracking.

15. Remove the cheesecake from the oven and cool completely at room temperature then cover and chill for at least 6 hours or overnight until very cold and firm.

16. For the ganache place the chocolate chips in a heatproof bowl. Heat 1/2 cup heavy cream until steaming then pour it over the chocolate and let stand for 2 to 3 minutes.

17. Add the light corn syrup if using and stir gently until the mixture is smooth shiny and pourable. Let it cool slightly so it thickens just a bit.

18. Release the chilled cheesecake from the springform pan and place it on a serving plate. Slowly pour the ganache over the top allowing it to drip over the edges.

19. While the ganache is still just slightly soft decorate the top with fresh cherries and sprinkle with dark chocolate shavings or curls.

20. Chill for 20 to 30 minutes to set the ganache then slice with a hot dry knife for clean layers and serve.