Before getting started, spray a 9×13 baking dish with nonstick cooking spray.
Melt the butter in a large sauce pan or Dutch oven over low to medium heat on the stovetop.
Add in the vanilla extract, salt, and mini marshmallows. Heat and stir the mixture until the marshmallows have completely melted.
Remove from the heat, and stir in the peanut butter.
Stir in the crispy rice cereal once the peanut butter is melted and fully stirred into the marshmallow mixture.
Spread the peanut butter and Rice Krispie treats into your baking dish, and gently press them down.*
Once they've cooled completely, cut into Rice Krispie squares and serve!