Step 1: Prepare the Crust

1. Preheat your oven to 350°F (175°C). Grease a 9-inch springform pan or line the bottom with parchment paper for easy removal.
2. In a mixing bowl, combine the crushed chocolate sandwich cookies with melted butter. Stir until the crumbs are evenly coated and have the texture of wet sand. If you prefer a sweeter crust, add the optional granulated sugar.
3. Press the mixture firmly into the bottom of the prepared pan, using the back of a spoon or a flat-bottomed cup to create an even layer.
4. Bake for 10 minutes, then remove from the oven and allow it to cool while preparing the filling.

Step 2: Make the Cheesecake Filling

1. In a large bowl, beat the softened cream cheese with granulated sugar until smooth and creamy. This step is crucial for preventing lumps in your batter.
2. Add vanilla extract and mix until well incorporated.
3. Beat in the eggs one at a time, mixing just until combined after each addition. Overbeating can introduce too much air into the batter, which may cause cracks during baking.
4. Fold in the sour cream and heavy cream, ensuring a smooth consistency.
5. Sift in the unsweetened cocoa powder and mix until fully combined.
6. Finally, pour in the melted dark chocolate and gently mix until the batter is rich and uniform in color.

Step 3: Bake the Cheesecake

1. Pour the prepared filling into the cooled crust, spreading it evenly.
2. To prevent cracks, place the springform pan inside a larger baking pan and fill the outer pan with hot water, about halfway up the sides of the cheesecake pan. This creates a water bath, which ensures even baking and a creamy texture.
3. Bake for 50-60 minutes, or until the edges are set but the center still has a slight jiggle. The cheesecake will continue to set as it cools.
4. Turn off the oven and leave the cheesecake inside with the door slightly open for an hour. This gradual cooling process helps prevent cracks.
5. Transfer the cheesecake to the refrigerator and chill for at least 4 hours, preferably overnight.

Step 4: Prepare the Cherry Topping

1. In a saucepan over medium heat, combine cherries, granulated sugar, cornstarch, and lemon juice.
2. Stir continuously until the mixture thickens, about 5 minutes. If using fresh cherries, allow them to release their juices before the sauce thickens.
3. Remove from heat and let it cool completely before spreading it over the cheesecake.

Step 5: Assemble the Cheesecake

1. Once the cheesecake is fully chilled, carefully remove it from the springform pan.
2. Spoon the cooled cherry topping over the surface, allowing some of the sauce to drip down the sides for a dramatic effect.
3. Garnish with dollops of whipped cream, chocolate shavings, and fresh cherries for a stunning final touch.