In a medium bowl, combine the instant vanilla pudding mix and cold milk. Whisk together for about 2 minutes until the mixture thickens. Stir in the vanilla extract.
In a large serving dish or individual cups, layer half of the sliced strawberries at the bottom.
Spoon half of the pudding mixture over the strawberries, spreading it evenly.
Add half of the sliced bananas on top of the pudding.
Sprinkle half of the crushed graham crackers over the bananas.
Repeat the layers with the remaining strawberries, pudding, bananas, and graham crackers.
Top with whipped topping, spreading it evenly over the final layer.
Chill in the refrigerator for at least 2 hours before serving to allow the flavors to meld.
Garnish with fresh mint leaves if desired before serving.