Grease a 9-inch square baking dish with butter or non-stick spray and set aside.
In a large pot over medium heat, melt the butter and 10 ounces of mini marshmallows, stirring until completely melted and smooth.
10 ounces mini marshmallows, 4 tablespoons unsalted butter
Stir in the peanut butter, vanilla extract and salt until fully combined.
½ cup creamy peanut butter, 1 teaspoon vanilla extract, ½ teaspoon fine sea salt
Remove the pot from the heat and gently fold in the Rice Krispies cereal until well coated with the marshmallow mixture.
6 cups Rice Krispies cereal
Gently fold in the extra 2 cups of mini marshmallows until evenly distributed.
2 cups mini marshmallows
Quickly transfer the mixture into the prepared baking dish. Use a spatula or wax paper to gently press the mixture evenly into the pan. Avoid pressing too firmly to keep the treats light and chewy.
Let the treats cool at room temperature for about an hour or until set. Once cooled, cut into squares and serve.