Preheat your oven to 325°F (163°C). Line the bottom of a 9-inch springform pan with parchment and lightly butter the sides.

In a bowl, stir together graham cracker crumbs, granulated sugar, and melted butter until the crumbs are evenly moistened. Press the mixture firmly across the bottom of the prepared pan to form an even crust. Refrigerate while making the next layer.

Warm heavy cream in a small saucepan until just simmering. Pour over semi-sweet chocolate chips in a heatproof bowl, let it sit for a minute, then stir until smooth and glossy.

Spread the chocolate ganache over the chilled crust in an even layer and set aside to cool.

In a large bowl, beat cream cheese until smooth and creamy. Add granulated sugar and beat until combined.

Add eggs one at a time, mixing gently after each addition. Pour in heavy cream and vanilla extract, mixing until silky. Pour the filling gently over the chocolate layer in the pan.

Place the springform pan on a baking sheet. Bake for about 50–60 minutes, or until the edges are set and the center still has a slight wobble.

Turn off the oven, crack the door, and let the cheesecake sit inside for 30 minutes to cool gradually. Then transfer to a wire rack to cool completely before chilling in the refrigerator for at least 4 hours, preferably overnight.

Warm heavy cream in a small saucepan until just simmering, pour over semi-sweet chocolate chips, let sit, and stir until smooth.

Allow the ganache to cool slightly so it thickens but remains pourable, then pour it over the chilled cheesecake, letting it drip a little over the sides. Chill again until set.