Line a 9x13 inch baking pan with parchment paper, ensuring the parchment is pressed into the corners.

In a large saucepan, melt 3 tablespoons of butter over medium heat. Add 10 ounces of marshmallows and stir until completely melted and smooth, about 3-5 minutes.

Remove the saucepan from heat and stir in 1/4 cup of key lime juice and a tablespoon of zest. Fold in 1 cup of graham cracker crumbs and then 6 cups of Rice Krispies until well-coated.

Transfer the mixture to the prepared pan and press down firmly to create an even layer without over-compressing.

Let the mixture cool at room temperature for 15-20 minutes, then refrigerate for at least 30 minutes to set.

Melt 4 ounces of white chocolate in a microwave-safe bowl, then drizzle it over the set treats. Allow the chocolate to harden before cutting into squares.