Line a 9"x9" or 8"x8" inch pan with foil, spray with cooking spray, set aside.
In a large pot over medium-low to low heat, melt the butter and 8 cups of the marshmallows. Once the marshmallows have just melted, stir in the salt and vanilla.
Remove the pot from the heat, stir in the rice Krispy cereal. Mix until the cereal is completely coated in the marshmallow mixture.
Stir in the remaining 2 cups of mini mallows.
Spoon the rice Krispy mixture into the lined pan. Press the mixture into the pan (don’t press too hard.. you don’t want it *too* compact).
Let set for 30 minutes-60 minutes.
When ready to serve, lift the foil from the pan and cut into squares.
Store at room temperature, covered or in an airtight container for 3-5 days.
Notes
Spray a wooden spoon, spatula, or your hands with nonstick cooking spray prior to pressing the gooey mixture into the pan. It will prevent it from sticking. Don’t press the mixture firmly into the pan. They’ll get hard and dry if you do. You want them to be light and gooey, so keep a soft touch when putting them in the pan.Store at room temperature in an airtight container or Ziplock bag (with the air pushed out of it) for 3-5 days to prevent the treats from drying out.Don’t store them in the fridge or else they will go hard and won’t soften back up at room temperature. (Same with freezing!)