Prepare Your Pan:

Lightly grease a 9x13-inch baking pan with cooking spray or a bit of butter.

Melt the Butter & Marshmallows:

In a large pot over medium heat, melt the butter. Once it’s fully melted, add the marshmallows. Stir constantly until the marshmallows melt into a smooth, creamy mixture. Remove from heat and stir in the vanilla extract, if using.

Mix in the Cereal:

Immediately stir in the Lucky Charms cereal. Work quickly to coat the cereal evenly before the mixture begins to cool and set.

Press into Pan:

Transfer the coated cereal mixture into your prepared pan. Use a buttered spatula or wax paper to gently press the mixture down evenly—don’t press too hard or they’ll turn out dense instead of chewy.

Cool & Slice:

Let the treats cool at room temperature for about 30 minutes. Once set, slice into squares and serve.