In a small bowl, combine the graham cracker crumbs, melted butter, and granulated sugar. Stir until all the crumbs are evenly coated with the butter.
Press the mixture firmly into the bottom and up the sides of a 9-inch pie pan, using the bottom of a measuring cup to create a smooth, even layer. Set aside.
Cheesecake Filling
In a large mixing bowl, use a hand mixer to beat the softened cream cheese and confectioners’ sugar together until the mixture is completely smooth.
Add the marshmallow fluff and vanilla extract, then mix again until fully incorporated.
In a separate bowl, pour in the heavy cream and begin whipping at low speed. Gradually increase to high speed as the cream thickens and forms stiff peaks. Keep a close eye on it to avoid over-whipping.
Carefully fold the whipped cream into the cream cheese mixture using a spatula, keeping the texture light and airy.
Pour the cheesecake filling over the prepared crust and spread it into an even layer. Smooth the top with a spatula. Place the cheesecake in the refrigerator to chill for at least 4 hours, or until completely set.
Once chilled, top the cheesecake with a layer of marshmallow whipped cream.
Finish by garnishing with mini marshmallows and crushed graham crackers just before serving.