In a large mixing bowl, beat the cream cheese and confectioners' sugar together with a hand mixer until smooth.
Add the marshmallow fluff and vanilla. Mix until combined.
Add heavy cream to a mixing bowl. Start mixing at the lowest speed, and then gradually increase the speed to high.
The cream will thicken and start to peak. Mix on high until the cream is thick and stiff. This happens quickly, so watch it closely.
Gently fold the whipped heavy cream into the cream cheese mixture and then pour over the prepared crust in an even layer. Use a spatula to smooth the top of the mixture. Chill the cake in the refrigerator for at least 4 hours, or until set.
Spread marshmallow whipped cream over the chilled cheesecake in a smooth layer.
Garnish with mini marshmallows and crushed graham crackers before serving.