In a mixing bowl, whisk together the cold milk and instant vanilla pudding mix until smooth and thickened, about 2 minutes.

In a serving dish, layer half of the vanilla pudding mixture, followed by half of the sliced bananas, and half of the Cool Whip.

Repeat the layers with the remaining pudding, bananas, and Cool Whip.

Crush some vanilla wafers and sprinkle on top for garnish. Refrigerate for at least 1 hour before serving.