Prepare the brownies according to box directions.
Line a 9x13" baking dish with parchment paper and then spray with cooking spray.
Spread the brownie batter in the prepared dish and bake 5 minutes less than package instructions.
Once baked, lightly press 2 cups of chopped Oreos into the warm brownies.
Let cool for 30 minutes. While cooling, set out the mint chip ice cream and Cool Whip to allow them both to thaw.
Once the ice cream is softened, I like to use a big spoon to mix it up and make it easier to spread. Spread the softened ice cream on top of the brownies.
In a large bowl, stir together the thawed Cool Whip and 1 cup of chopped Oreos.
Spread the Oreo Cool Whip on top of the ice cream layer.
Warm the hot fudge by either putting it in a small pot of simmering water until warmed, or microwave in 20 second intervals until warmed, stirring between each interval.
Drizzle the hot fudge over the Cool Whip layer, and then sprinkle with remaining chopped Oreos.
Cover with plastic wrap and then foil, and place in the freezer for at least 4 hours.
Once frozen, cut into bars. Enjoy!