Prepare the vanilla pudding according to package instructions.
In a mixing bowl, combine milk, sugar, cornstarch, and salt over medium heat.
Stir continuously until thickened, then remove from heat and add vanilla extract.
Let the pudding cool slightly, then fold in half of the whipped cream.
Layer the bottom of a cake pan with vanilla wafers.
Slice bananas and place half on top of the wafers.
Spread half of the pudding mixture over the bananas.
Add another layer of vanilla wafers and repeat the banana and pudding layers.
Top with the remaining whipped cream and garnish with banana slices.
Cover and refrigerate for at least 4 hours before serving.