In a large bowl, combine the 1/2 of the Cool Whip with the Karo syrup, the banana extract and the sweetened condensed milk. Set aside.
In a different (large) bowl, prepare the vanilla pudding mix according to box instructions by adding milk to the pudding. Add in the banana pudding mix, and the remaining milk, and beat until pudding is well mixed and smooth. Add this to the Cool Whip mixture.
In a deep dessert dish, a large pan or bowl (whatever you choose to layer this in - you should be able to make at least 3 layers) cover the bottom of the dish with a single layer of vanilla wafers. Place some of the sliced bananas on top of the wafers, then cover with pudding mixture.
Repeat Step 3 layers until you reach the top of the dish. Top with remaining Cool Whip. Garnish with a few banana slices and a few vanilla wafers.
Chill overnight so the cookies can soften and enjoy!