Prepare the Crust:

1. Preheat the Oven: Preheat your oven to 325°F (163°C).
2. Make the Graham Cracker Crust: In a medium bowl, combine the graham cracker crumbs, sugar, and melted butter. Stir until the crumbs are evenly coated and the mixture resembles wet sand.
3. Press the Crust into the Pan: Press the mixture into the bottom of a 9-inch springform pan. Use the back of a spoon to pack it tightly and evenly.
4. Bake the Crust: Bake the crust for 10 minutes, then remove from the oven and let it cool while you prepare the filling.

Make the Cheesecake Filling:

5. Beat the Cream Cheese: In a large mixing bowl, beat the softened cream cheese with an electric mixer until smooth and creamy.
6. Add Sugar and Vanilla: Add the sugar and vanilla extract, continuing to beat until well combined.
7. Add Eggs: Add the eggs one at a time, mixing well after each addition.
8. Add Sour Cream and Heavy Cream: Stir in the sour cream and heavy cream until the mixture is smooth and creamy.
9. Pour the Filling into the Pan: Pour the cheesecake filling into the cooled crust, smoothing the top with a spatula.

Bake the Cheesecake:

10. Bake the Cheesecake: Bake the cheesecake at 325°F (163°C) for 50-60 minutes, or until the edges are set and the center is slightly jiggly. Turn off the oven and leave the cheesecake inside for 1 hour.
11. Cool the Cheesecake: After the hour, remove the cheesecake from the oven and let it cool to room temperature before placing it in the refrigerator for at least 3 hours (or overnight) to fully set.

Prepare the Topping:

12. Melt the Chocolate: While the cheesecake is chilling, melt the chocolate chips in a microwave-safe bowl in 20-second intervals, stirring each time until smooth.
13. Toast the Marshmallows: Once the cheesecake is chilled, sprinkle the mini marshmallows evenly on top. Use a kitchen torch to toast them lightly, or place the cheesecake under a broiler for a few seconds (watch carefully to avoid burning).
14. Drizzle with Chocolate: Drizzle the melted chocolate over the toasted marshmallows. If desired, sprinkle the crushed graham crackers on top for extra texture and flavor.