Step 1: Grease a 9-inch springform pan with butter or cooking spray. Line the bottom with parchment paper for easy removal, if desired.
Step 2: In a large, microwave-safe bowl, melt 1/2 cup (1 stick) unsalted butter. Add 10 ounces of mini marshmallows and stir until completely melted and smooth. Alternatively, melt butter and marshmallows in a large pot over medium-low heat.
Step 3: Remove from heat and quickly stir in 6 cups of Rice Krispies cereal until fully coated.
Step 4: Press the Rice Krispie mixture evenly into the bottom of the prepared springform pan. Use a piece of parchment paper or buttered hands to press it down firmly and create a compact, even crust. Set aside to cool and firm up while you prepare the filling.
Step 5: In a large mixing bowl, beat 16 ounces of softened full-fat cream cheese with 1 cup of powdered sugar until smooth and creamy. Ensure there are no lumps.
Step 6: Add 1 teaspoon of vanilla extract and 1/4 teaspoon of salt to the cream cheese mixture, beating until just combined.
Step 7: In a separate, very cold bowl, whip 1 1/2 cups of cold heavy cream until stiff peaks form. Be careful not to over-whip.
Step 8: Gently fold the whipped cream into the cream cheese mixture using a spatula, until no streaks remain. Do this in two additions to maintain the airiness.
Step 9: Pour the cheesecake filling over the cooled Rice Krispie Treat crust in the springform pan. Smooth the top with an offset spatula or the back of a spoon.
Step 10: Cover the cheesecake loosely with plastic wrap and refrigerate for at least 6 hours, or preferably overnight, to allow it to set completely.
Step 11: Once chilled, carefully remove the sides of the springform pan. If using parchment paper on the bottom, you can slide it onto your serving platter.
Step 12: Garnish with extra mini marshmallows, sprinkles, chocolate shavings, or a drizzle of chocolate fudge sauce just before serving.