1-First Step: Prep and pan setup Grease a 9×13 inch pan with cooking spray or butter. If you want thicker bars, prepare two 8×8 pans instead. Line the pan with parchment paper if you prefer easy removal and neater edges. Measure out your cereal into a large bowl so everything is within reach.

2-Second Step: Melt the butter Place a large pot over low heat and add 1/2 cup unsalted butter. Melt slowly and watch carefully; low heat prevents browning or burning. If you want to add 1/2 teaspoon salt, stir it into the melting butter to distribute flavor evenly.

3-Third Step: Melt the marshmallows Once the butter is melted, add the entire 16 oz bag of mini marshmallows. Stir constantly with a rubber spatula to help the marshmallows melt into a smooth, glossy mixture. Keep the heat low. If you are using large marshmallows, allow 1-2 extra minutes for them to melt fully. Avoid rushing by turning the heat up that can scorch the mixture.

4-Fourth Step: Combine cereal and marshmallow mixture Remove the pot from heat as soon as the marshmallows are melted. Gently fold in the 11.5 oz cereal, using a spatula to coat without crushing the cereal. Work quickly but gently the marshmallow mix firms up as it cools. If you are adding optional mix-ins (chocolate chips, sprinkles, or candy pieces), fold them in here in small amounts so they stick without melting.

5-Fifth Step: Transfer to pan and press Pour the cereal-marshmallow mixture into the prepared pan(s). Grease your hands or a spatula with a touch of butter or cooking spray to prevent sticking. Press the mixture into an even layer using a parchment-topped surface or the back of a lightly greased spatula. Press gently do not compact heavily. Pressing too hard creates dense, tough bars instead of light and fluffy treats.

6-Final Step: Cool and serve Allow the pan to cool completely at room temperature before cutting into squares. Cooling usually takes about 1 hour. Once set, cut into about 16 bars. Store leftovers in an airtight container at room temperature for 2-3 days, or freeze for up to 2 months.