Preheat the oven to 350°F. In a mixing bowl, combine graham cracker crumbs, sugar, and melted butter. Press into the bottom of a greased 9-inch springform pan. Bake for 10 minutes, then cool completely.
In a large bowl, beat the softened cream cheese with sugar until smooth. Add vanilla extract and marshmallow fluff, mixing until well combined.
In a separate bowl, whip the heavy cream to stiff peaks. Gently fold the whipped cream into the cream cheese mixture.
Pour the filling over the cooled crust and spread evenly. Refrigerate for at least 4 hours or overnight.
Top the set cheesecake with mini marshmallows and drizzle melted chocolate (if using) before serving.
