Prepare a 9x9 (or 8x8) square baking pan. Line with 2 parchment papers diagonally, leaving some overhang on all sides. Set aside.
In a large pot over medium-high heat, add the cereal until they started to smell toasted, about 3 - 4 minutes, stirring frequently. Transfer to a large bowl to set aside.
Line a medium baking sheet with aluminum foil. Set the baking sheet on a trivet. Clear the surrounding area. Add ½ cup marshmallows in center of the baking sheet in a single layer. Using a kitchen torch, toast the marshmallows until golden brown or slightly burnt. Be extra careful, the marshmallow can catch on fire very easily. If that happens, carefully and quickly blow off the fire. Set the marshmallows aside. If no kitchen torch, skip the toasting part.
In the same large pot, wipe clean with wet paper towels. Set over medium-low heat, melt the butter. Add 3½ cups marshmallows and cook until melted and smooth, stirring continuously. Stir in the salt.
Reduce the heat to low. Add the toasted cereal and stir gently until evenly coated. Remove from heat. Stir in graham cracker pieces and chocolate chips. Last, stir in most of the toasted marshmallows (or untoasted ones if no kitchen torch). Leave a few for topping.
Transfer the mixture to the prepared pan. Using a rubber spatula, gently spread mixture to fit the pan. Sprinkle the reserved toasted marshmallows, optional graham cracker and optional chocolate chip on top if using. Press down the mixture with the spatula. Set aside to cool for at least 2 hours or until the chocolate chips have set.
Use the parchment paper overhangs to lift the entire treat out of the pan. Place on a cutting board and cut into 9 big squares. Serve.