Preheat your oven to 325°F.
In a medium bowl, combine graham cracker crumbs, melted butter, and granulated sugar. Mix until well combined.
Press the mixture firmly into the bottom of a 9-inch springform pan to form the crust.
Bake for 10 minutes, then remove from the oven and let cool.
In a large mixing bowl, beat the softened cream cheese with an electric mixer until smooth.
Gradually add the powdered sugar and vanilla extract, mixing until well combined.
Fold in the mini marshmallows.
In a separate bowl, whip the heavy cream until stiff peaks form.
If using gelatin, dissolve it in cold water and let it sit for 5 minutes, then gently heat until melted and add to the whipped cream.
Fold the whipped cream into the cream cheese mixture until fully combined.
Pour the cheesecake filling over the cooled crust and smooth the top with a spatula.
Refrigerate for at least 4 hours or until set, preferably overnight for the best texture.
To serve, carefully remove the sides of the springform pan. Slice and enjoy your delicious marshmallow cheesecake!