In a microwave-safe bowl, melt the butter and marshmallows for 3 minutes, stirring halfway through. Add the mixture to the cereal and stir until well combined. Let cool slightly.
Line a 13-by-9-inch baking pan with a long sheet of parchment paper to create two overhangs to use as handles later. Spray the parchment paper with cooking spray. Press half of the treat mixture into the base of the baking dish. Use the paper overhang to lift and transfer the giant crispy treat to a baking sheet. Repeat with the remaining half-batch of crispy treats, leaving it in the pan to create a base layer.
Top the base layer with the marshmallow spread and smooth it into an even layer. Top with the ice cream and smooth it out evenly. Top with the second layer of crispy treats.
Freeze until firm, about 4 hours or overnight. Melt the chocolate chips in a microwave-safe bowl in 30-second intervals, stirring in between each, until smooth. Turn the frozen crispy treat out onto a piece of parchment paper and cut into rectangular sandwiches, using a chef’s knife dipped in hot water. Dip and wipe the knife between each cut for even edges. Dip the end of each sandwich into the melted chocolate, then roll in the peanuts. Wrap each treat in parchment paper and store in the freezer until ready to serve.