Chill your mixing bowl and whisk in the fridge for 10 minutes if your kitchen is warm.

In a large bowl, pour in 3 cups of cold milk and add the two boxes of instant banana cream pudding. Whisk together until smooth, then continue whisking for about 1 minute until the mixture starts to thicken.

Fold in one 8-ounce container of whipped topping gently until the filling is uniform and fluffy. Set this pudding mixture aside.

Line the bottom of a 9×13 baking dish with about one-quarter of the graham crackers.

Spread 1/3 of the pudding mixture over the cracker layer and smooth with an offset spatula. Repeat two more times: crackers, pudding, crackers, pudding.

Finish with the remaining graham crackers on top and spread the remaining container of whipped topping over the top layer so no graham crackers are exposed.

Cover with plastic wrap and refrigerate for at least 6 hours; overnight chilling is recommended.

Before serving, top with crushed leftover graham crackers and fresh banana slices.

Slice with a sharp knife and serve chilled.