Prepare the crust by preheating the oven to 350°F (175°C).
In a medium bowl, combine the graham cracker crumbs and melted butter until well mixed.
Press the crumb mixture into the bottom of a springform pan and bake for 10 minutes.
While the crust cools, melt the dark chocolate in a microwave or double boiler until smooth.
In a large mixing bowl, beat the softened cream cheese and sugar until light and fluffy.
Add the melted chocolate and vanilla extract to the cream cheese mixture and mix until combined.
Add eggs, one at a time, mixing well after each addition until fully incorporated.
Fold in the sour cream and fresh raspberries gently using a spatula.
Pour the mixture over the cooled crust in the springform pan and smooth the top.
Bake in the preheated oven for 50-60 minutes or until the edges are set but the center still jiggles slightly.
Once baked, turn off the oven and crack the door slightly, allowing the cheesecake to cool in the oven for an hour.
After an hour, remove the cheesecake from the oven and let it cool at room temperature before refrigerating for at least 4 hours or overnight.
Before serving, garnish with additional raspberries and a drizzle of melted chocolate if desired.