Prep your pan: Grease a 9x13-inch baking pan with nonstick spray or a thin layer of butter. Line with parchment for easy lifting, if you have it.

Measure and set aside: Pour 6 cups of cereal into a large mixing bowl. Reserve 1 cup of mini marshmallows in a separate small bowl for later folding.

Melt the butter low and slow: In a large pot over low heat, melt 6 tablespoons butter. Don’t rush this; gentle heat prevents a tough final texture.

Add most of the marshmallows: Stir in the 10-ounce bag of mini marshmallows (minus the 1 cup you reserved). Keep the heat on low and stir constantly until fully melted and smooth.

Flavor it: Remove from heat. Stir in vanilla and a generous pinch of salt. Taste a tiny bit (careful—it’s hot) and adjust salt if desired.

Combine with cereal: Pour the melted marshmallow mixture over the cereal. Use a greased spatula to fold gently until about 80% combined.

Fold in the reserved marshmallows: Add the extra cup of mini marshmallows and fold just until evenly distributed. This creates soft, gooey pockets throughout.

Press into the pan: Transfer the mixture to your prepared pan. Lightly grease your hands or a spatula, then press the mixture into an even layer. Do not pack it hard—a light press keeps the bars airy and chewy.

Let set: Allow the treats to rest at room temperature for 30–45 minutes, or until firm enough to slice. For faster setting, chill for 10–15 minutes, but avoid over-chilling.

Slice and serve: Lift from the pan (if lined) and cut into squares with a sharp knife. Wipe the knife between cuts for neat edges.