1. Set the 2 tubs of ice cream on the counter while you prepare the cinnamon cereal and allow it to soften slightly. Prepare a 9-inch square baking pan by lining it with parchment paper or aluminium foil and spraying with non-stick pan spray.  Also, prepare and set aside a second sheet of parchment or foil of the same size. In a large pot, melt the butter, add the marshmallows, and stir until melted.  Add the cinnamon cereal and continue stirring gently until fully mixed.
2. Pour 1/2 of the cereal and marshmallow mixture into the pan and press down lightly. When you feel you have a cohesive square, slide it out of the pan using the parchment or foil to pull it out.  Place the second piece of parchment or foil into the pan and spray with non-stick pan spray.  Dump the remaining cereal marshmallow mixture in and press it gently into the bottom of the pan. Add the 2 tubs of ice cream and smooth it over the marshmallow cereal layer.
3. Place the other cereal and marshmallow layer on top of the ice cream, pressing down lightly so that everything is level with the top of the pan.  Cover the pan and put it in the freezer for at least an hour.
4. Remove from the freezer and slide the bars out of the pan using the foil or parchment pan liner.  You might need to use a knife or spatula to loosen the edges or to help support the bottom of the bars while you lift them out. Slide them onto a cutting board and cut into squares or bars. Wrap each bar individually in wax paper, parchment, or plastic wrap and return to freezer. Or, serve and enjoy!
5. Optional: Melt the 1/2 cup of chocolate chips in the microwave in 20-second bursts until fully melted, and drizzle over the sliced bars. The chocolate should freeze on contact, but if it doesn’t, return them to the freezer for 5 minutes before wrapping.

Original recipe by Ben & Jerry’s.