• Step 1: In a large microwave-safe bowl, melt the butter and marshmallows together in the microwave, stirring every 30 seconds, until completely smooth and melted, about 2 minutes total.
• Step 2: Remove the bowl from the microwave and stir in the vanilla extract until well combined.
• Step 3: Gently fold in the Lucky Charms cereal, making sure to coat all the pieces evenly with the marshmallow mixture.
• Step 4: Grease a 9×13-inch baking dish and transfer the Lucky Charms mixture to the dish, pressing it into an even layer.
• Step 5: Allow the treats to cool completely at room temperature before cutting into squares and serving.