# How-To Steps:
01 - Grease a 9x13-inch baking pan with butter or nonstick spray.
02 - Melt the unsalted butter in a large saucepan over low heat.
03 - Add mini marshmallows to the melted butter, stirring constantly until smooth and fully melted.
04 - Remove from heat and stir in vanilla extract and salt, if using.
05 - Immediately add the Rice Krispies cereal to the marshmallow mixture and gently fold until evenly coated.
06 - Quickly transfer the mixture into the prepared pan and press evenly using a buttered spatula or wax paper, being careful not to press too firmly for soft texture.
07 - Allow to cool for at least 30 minutes before cutting into 12 bars.