In a small microwave safe bowl, combine the chocolate, milk, and butter. Microwave in 30 second intervals, stirring each time, until chocolate is melted and smooth.

In another bowl, whisk together the milk and instant vanilla pudding according to package directions. Place the bowl in the fridge so the pudding can set up for 5 minutes.

Spread the melted chocolate over the bottom of the pie crust. Place banana slices in a single layer on top of the chocolate. Spread pudding over top. Place another single layer of banana slices on top of the pudding.

In the bowl of an electric mixer fitted with the whisk attachment, whisk the whipping cream and powdered sugar on high speed until cream holds stiff peaks. Spread the cream on top of the pie (you'll likely have a bit leftover--save it for topping berries or adding to your favorite hot chocolate!)

Place the pie in the fridge to set up for at least 2 hours. Serve within 24 hours.