Grab a jelly roll pan (10x15-inch) and line with foil then lightly spray with nonstick cooking spray. Set aside.
Add butter to dutch oven or large pot and melt place over medium-low heat.
Set 4 cups of marshmallows to the side for later and add the rest to the melted butter pot. Stir constantly until all is melted and combined.
Remove the mixture from the heat. Add salt and stir.
Add vanilla extract and well to combine.
Add half of the Rice Krispies cereal to the mixture. Stir to combine.
Add the rest of the cereal and reserved marshmallows to the mix. Stir to combine.
Transfer the mixture to the prepared jelly roll pan.
Use nonstick cooking spray to lightly spray your hands and carefully press the treat mixture into the pan. You do not want to smash the mixture down, just simply form it to the shape of the pan.
Let them set up for at least 2 hours. Cut into bars and serve!
Notes
I use salted butter and additional salt in the recipe to help cut down on the sweetness. It helps balance the treat bars out and really helps set these bars apart. But you can certainly leave out the additional salt.
You can change up the texture even more by adding some mix-ins. Try using: chopped nuts or candy bars, mini chocolate chips, or sprinkles.
No jelly roll pan? No problem, make thicker bars in a 9x13-inch baking dish instead.