01 -
Spray a 9×13-inch pan with non-stick spray for easy cleanup, then put it aside until needed.
02 -
Toss the crispy rice cereal with 5 or 6 graham cracker pieces in a large bowl and keep this on the side for later.
03 -
Over low heat in a big saucepan, melt down the butter. Once melted, add 8 cups of marshmallows and stir continuously until smooth and gooey.
04 -
Turn off the heat, then mix in the juice (around 1½ tablespoons) and zest (2 teaspoons) from 4 key limes into the marshmallow mix.
05 -
Pour the cereal-graham mix into the marshmallow mixture, along with the 2 leftover cups of marshmallows. Mix everything well but don't worry about the marshmallows melting completely for a nice chewy touch.
06 -
Press the mix evenly into your prepped dish using a rubber spatula sprayed with non-stick spray. Scatter the rest of the graham cracker crumbs over the top and gently press them in.
07 -
Microwave the white chocolate and oil in a heatproof bowl for 30 seconds, stir, and zap for another 30 seconds if needed. Mix 1 teaspoon of lime zest (from 1-2 limes) into the melted chocolate.
08 -
Drizzle the lime-flavored white chocolate over the bars, then let them rest for at least 30 minutes to an hour before slicing.