Preheat oven to 350°F (175°C).

In a medium bowl, combine chocolate cookie crumbs, melted butter, and sugar. Press mixture evenly into the bottom of a 9-inch springform pan.

Bake for 10 minutes. Let cool completely.

In a large bowl, beat softened cream cheese until smooth. Gradually add sugar and beat until well combined.

Beat in eggs one at a time, mixing well after each addition.

Stir in heavy cream, cocoa powder, and vanilla extract until just combined. Do not overmix.

Pour the filling over the cooled crust.

In a small saucepan, combine fresh raspberries, sugar, and lemon juice. Cook over medium heat, stirring occasionally, until raspberries break down and the mixture thickens into a sauce.

Strain the raspberry sauce through a fine-mesh sieve to remove seeds. Let cool slightly.

Drizzle spoonfuls of raspberry sauce over the cheesecake filling. Use a toothpick or knife to swirl the sauce into the filling.

Bake at 350°F (175°C) for 55-65 minutes, or until the edges are set and the center is slightly jiggly.

Turn off the oven and let the cheesecake cool in the oven with the door ajar for 1 hour.

Remove from oven and let cool completely at room temperature. Then, cover and refrigerate for at least 4 hours, or preferably overnight.

Place chopped dark chocolate in a heatproof bowl.

Heat heavy cream in a small saucepan until simmering. Pour hot cream over the chocolate and let it sit for 5 minutes.

Whisk until smooth and glossy.

Let the ganache cool slightly, then drizzle over the chilled cheesecake.

Garnish with fresh raspberries before serving.