Cut one round of parchment paper to fit an 8-inch round metal cake pan. Place parchment round in bottom of pan. Pre-heat oven according to brownie mix instructions (typically 350 degrees Fahrenheit).
Prepare brownie mix according to directions on box. (Choose recipe to make an 8-inch square or round pan.) Don’t over beat. Pour brownie batter into prepared pan.
Bake brownies for 25 minutes (NOTE: this is significantly shorter than the mix directions.) Let brownies cool on a wire rack. When cool, remove brownies from pan, wrap in plastic wrap and put back in pan.
While brownies are baking, line second pan with plastic wrap. Remove mint chocolate chip ice cream from container and smash ice cream into plastic lined pan. Press firmly to fill pan and remove air bubbles. Wrap plastic wrap completely over ice cream and freeze both ice cream and brownie pans for at least two hours.
To assemble, remove brownie round from pan and place on cake plate. Remove ice cream round from pan and place atop brownie round.
Working quickly, use a narrow metal spatula to spread whipped topping over cake sides and top. It should spread easily. If desired, place a small amount of whipped topping in a pastry bag and decorate top with swirls or a shell border. Decorate with Andes Mints.
Place cake back in freezer until ready to serve. To cut the cake, use a French Chef’s Knife or other heavy, sharp knife. You will need to press hard to get through the brownie portion. Because you didn’t cook it completely, you will be able to cut through the brownie.