Prepare the crust: In a medium bowl, combine 1 1/2 cups graham cracker crumbs, 1/3 cup melted butter, and 1/4 cup sugar. Mix until the crumbs are evenly coated with butter. Press the mixture firmly into the bottom of a 9-inch springform pan. This will be the base for your cheesecake.
Make the filling: In a large mixing bowl, beat together 8 oz softened cream cheese, 1 cup marshmallow fluff, 1/2 cup powdered sugar, and 1 tsp vanilla extract using an electric mixer. Beat until the mixture is creamy and smooth, ensuring there are no lumps.
Fold in the whipped cream: Gently fold 1 1/2 cups whipped cream into the cream cheese mixture. Use a spatula to combine the ingredients without deflating the whipped cream too much. The mixture should be light and fluffy.
Assemble the cheesecake: Spread the creamy filling evenly over the prepared graham cracker crust. Smooth the top with a spatula.
Refrigerate: Cover the cheesecake with plastic wrap and refrigerate for at least 4 hours (or overnight) to allow it to set. The longer you refrigerate, the firmer the cheesecake will be.
Add the topping: Just before serving, remove the cheesecake from the refrigerator and top it with mini marshmallows. You can toast them lightly with a kitchen torch for a fun twist!