Take the ice cream out of your freezer and let it sit on the countertop for about 30 minutes to soften.
Meanwhile, melt the butter in a skillet over medium heat. Add the crushed cereal, sugar and cinnamon, and cook, stirring frequently, until golden brown, 3-5 minutes.
Transfer half of the cereal mixture to a 9-by-13-inch baking dish and spread it in an even layer to cover the bottom of the pan.
In a large mixing bowl using a rubber spatula, stir together the softened ice cream and whipped topping. Transfer this mixture to the baking dish and spread it into an even layer over the cereal layer.
Top with the remaining cereal mixture, spreading it in an even layer over the top of the ice cream mixture. Cover and freeze for 6 hours or longer, until completely frozen.
To serve, cut into squares and drizzle chocolate sauce or caramel sauce over the top. Add a dollop of whipped topping if desired.