Whisk together instant vanilla pudding mix with milk until smooth. Scrape bottom of bowl and stir. Add heavy cream. Whip with an electric mixer on high speed until light and fluffy, about 45 seconds.
Stir in banana slices and nilla wafers. Spread filling into the graham cracker crust. If any banana slices are visible, spread a little filling over them to prevent browning. Chill pie for four hours.
Combine heavy cream with powdered sugar, and vanilla extract in a medium bowl. Whip until stiff peaks form, about two minutes on high speed. Spread whipped cream over the pie.
Instant Pudding. Use instant pudding. Cook and serve pudding doesn’t work in this recipe.
Whipped Cream. Replace the whipped cream with 2 cups of whipped topping.
Nilla Wafers. If you want, break up a few of the cookies before stirring them into the filling.
Chill Time. It’s important to chill the pie for about four hours before serving. Doing this gives the cookies time to soften.