Line a 13x9-inch pan with parchment paper. Fill the bottom of the pan with IT'S-ITs. Scoop ice cream evenly to cover the sandwiches and spread to form a second layer of the casserole. Spread the whipped topping over the ice cream to create a third layer. Cover the top with crushed cookies, chocolate chunks and chocolate sauce. Freeze for 6 to 24 hours. Garnish with mint. Serve and enjoy!