Preheat the oven to 325°F (163°C). In a medium bowl, combine graham cracker crumbs and melted butter. Press mixture into the bottom of a 9-inch springform pan to form the crust.
In a large bowl, beat cream cheese and sugar until smooth. Add eggs one at a time, beating well after each addition.
Add melted chocolate and vanilla extract to the cream cheese mixture and blend until uniform.
Fold whipped heavy cream gently into the chocolate mixture until fully combined.
Pour the filling over the crust in the springform pan and smooth the top. Bake for 10 minutes, then turn off the oven and leave the cheesecake inside to set for about 1 hour.
Chill the cheesecake in the refrigerator for at least 4 hours before serving.
Notes
For best results, use high-quality chocolate and allow the cheesecake to chill overnight.