Preheat oven to 325 degrees F and grease a 9-inch cake pan with non-stick cooking spray.
In a medium bowl, combine graham cracker crumbs, melted butter, vanilla extract, and brown sugar; press evenly into the bottom and sides of the prepared pan.
Evenly spread mini marshmallows and mini chocolate chips over the crust.
Beat cream cheese until light and fluffy, then mix in sugar, corn starch, vanilla extract, and eggs.
Fold in sour cream and heavy cream until well combined.
Pour cheesecake batter over the crust evenly.
Place cake pan into a large roasting pan filled halfway with water to create a water bath.
Bake for 90-95 minutes until set, then open oven door and let cheesecake rest inside for 10 minutes before removing.
Allow cheesecake to cool completely.
Preheat oven broiler; spread heated hot fudge sauce over cheesecake and top with mini marshmallows.
Broil marshmallows for 1-2 minutes until lightly toasted.
Store cheesecake in the refrigerator.