Lightly coat your loaf pan or baking dish with cooking spray.

If you're making giant cereal bars like we did, use two loaf pans. If you'd rather have traditional squares, a 9x13-inch pan works perfectly.

In a large pot over medium-low heat, melt the butter completely.

Avoid using high heat, as it can make the marshmallows tougher.

Add the mini marshmallows to the melted butter.

Stir continuously until the mixture becomes completely smooth and creamy.

Gradually stir the Trix cereal into the melted marshmallow mixture a few cups at a time.

Mix gently until every piece of cereal is coated.

Transfer the mixture into your prepared pan.

Using a lightly buttered spatula or wax paper, gently press the cereal into an even layer.

Avoid packing it too tightly, or the treats may become dense instead of soft and chewy.

Allow the treats to cool completely at room temperature.

Once firm enough to slice, remove from the pan.

If using loaf pans, cut each loaf into one giant cereal bar or several smaller pieces.