1. Preheat your oven to 350°F (175°C). Line the bottom of a 9 inch springform pan with parchment paper and lightly grease the sides.

2. Combine the chocolate cookie crumbs, granulated sugar, and melted butter in a medium bowl. Stir until the crumbs are evenly moistened, then press firmly into the bottom of the prepared pan. Bake for 8 to 10 minutes, until fragrant, then reduce the oven temperature to 325°F (163°C). Let the crust cool slightly.

3. Make the chocolate cheesecake layer by beating the softened cream cheese and granulated sugar together until smooth and fluffy. Add cocoa powder and salt and mix until combined. Blend in sour cream, melted dark chocolate, and vanilla extract.

4. Add the eggs to the chocolate cheesecake batter one at a time, mixing on low speed just until each egg is incorporated. Do not overmix. Pour the chocolate cheesecake batter over the cooled crust and smooth the top.

5. Prepare the cherry layer by combining the cherries, granulated sugar, lemon juice, and 2 tablespoons of the water in a small saucepan. Cook over medium heat until the cherries soften and release their juices.

6. Stir the cornstarch into the remaining 2 tablespoons water to make a slurry. Add it to the cherry mixture and simmer for 1 to 2 minutes, stirring, until thickened and glossy. Remove from the heat and stir in the kirsch if using. Let cool until just warm.

7. Spoon the cooled cherry mixture evenly over the chocolate cheesecake layer, spreading it to the edges without pressing down too hard.

8. For the vanilla cheesecake layer, beat the softened cream cheese and granulated sugar together until smooth. Add sour cream and vanilla extract and mix until creamy.

9. Add the eggs to the vanilla cheesecake batter one at a time, mixing on low speed just until combined. Gently pour the vanilla batter over the cherry layer and smooth the top with an offset spatula.

10. Place the springform pan on a baking sheet. Set a separate pan of hot water on the rack below the cheesecake to create steam while it bakes.

11. Bake the cheesecake at 325°F (163°C) for 55 to 65 minutes, until the edges are set and the center still has a slight wobble. Turn off the oven, crack the door open, and let the cheesecake rest inside for 30 minutes.

12. Remove the cheesecake from the oven, run a thin knife around the inside edge of the pan, and let it cool completely at room temperature. Cover and refrigerate for at least 4 hours or overnight until fully chilled and set.

13. Make the ganache by heating the heavy cream in a small saucepan just until steaming. Pour it over the semi sweet chocolate chips in a heatproof bowl and let sit for 1 minute.

14. Stir the cream and chocolate together until smooth and glossy, adding corn syrup if you want extra shine. Allow the ganache to cool until it thickens slightly but is still pourable.

15. Release the chilled cheesecake from the springform pan and transfer it to a serving plate. Pour the ganache over the top, nudging it gently toward the edges so it drips down the sides.

16. Garnish the cheesecake with fresh whole cherries and chocolate shavings. Slice with a hot, clean knife, wiping the blade between cuts, and serve chilled.