Prep the pan. Lightly grease an 8x8 or 9x9-inch baking pan with nonstick spray or butter. For easier removal, line it with parchment, leaving overhang on two sides.

Measure first. Pour the crispy rice cereal into a large mixing bowl and set aside. Open the marshmallows and have them ready to go.

Melt the butter low and slow. In a large pot over low heat, melt the butter. Don’t rush this step. Low heat keeps the mixture silky and prevents stiff bars.

Add marshmallows. Stir in the marshmallows and keep the heat on low. Stir constantly until fully melted and smooth, 2–4 minutes. Remove from heat.

Flavor it. Stir in the vanilla and salt while the mixture is still warm. Taste for balance—just a hint of salt makes a big difference.

Combine with cereal. Immediately pour the marshmallow mixture over the cereal in the bowl. Use a greased spatula to fold until every piece is coated. Work quickly before it sets.

Press into the pan. Transfer to the prepared pan. With a greased spatula or your clean, buttered hands, press gently into an even layer. Don’t pack it down too firmly, or the treats will be dense.

Set and slice. Let cool at room temperature for 30–45 minutes. Lift out using the parchment overhang and slice into squares with a sharp knife.

Serve. Enjoy slightly warm for maximum gooeyness, or fully cooled for tidy squares.