Preheat oven to 350°F. With non-stick spray, lightly spray the bottom only of a light-colored metal 9'' x 13'' pan.

In a large bowl, with an electric mixer, beat the cake mix, flour, water, oil, and egg whites on low speed for 30 seconds. Scrape bowl well, then turn mixer up to medium speed and beat for 2 minutes more. It's ok if the batter is a bit lumpy. Stir in the creme de menthe syrup. Pour batter into prepared pan and spread into an even layer.

Bake for 28-30 minutes, or until toothpick inserted in center comes out just clean. Top of cake should be slightly mounded, with a very small amount of browning. Set cake on a rack to cool completely.

Once cake has cooled, gently spread fudge topping very evenly over the cake. If your hot fudge has been in the fridge, be sure to let it come to room temperature first, so it spreads easier.

In a medium bowl, gently fold together Cool Whip and creme de menthe syrup. Spread mixture evenly over the fudge layer.

Cover the pan with a tight-fitting lid and let the cake chill in the refrigerator for at least a couple hours before serving for the best flavor and texture. If desired, garnish individual pieces of cake with chopped Andes Mints.