In a medium bowl, whisk together the instant vanilla pudding mix and milk until smooth. Let it sit for about 5 minutes to thicken.

In another bowl, whip the heavy cream, powdered sugar, and vanilla extract until stiff peaks form.

Gently fold half of the whipped cream into the pudding mixture until combined. Reserve the other half for topping.

Layer half of the sliced bananas on the bottom of the graham cracker pie crust. Pour half of the pudding mixture over the bananas, then add the remaining banana slices and top with the rest of the pudding mixture.

Spread the reserved whipped cream over the top of the pie. If desired, sprinkle with ground cinnamon for added flavor.

Cover the pie with plastic wrap and refrigerate for at least 2 hours before serving to allow it to set.