Make or use a store-bought gluten free pie crust. (*See note) Preheat your oven to 350º F.
In a saucepan, add the milk, sugar, flour, and salt. Whisk and cook on medium heat until it gets a slightly bubbly. (Make sure to keep whisking constantly to avoid it burning on the bottom). Turn the heat to low.
Put the 3 egg yolks in a mug or heat-safe container (not plastic). Take a spoon and add a spoonful of hot liquid to the eggs and mix quickly. Repeat 3x with the hot liquid to temper your eggs. Once the eggs are tempered you can pour them into the pot and whisk.
Add the butter and vanilla and keep whisking. Turn the stove off and move the pan to a cool burner to allow some cooling.
Slice 3 bananas (the fourth banana is for the top of the pie). Layer the banana slices in the pie crust.
Pour the pudding mixuture over the bananas and bake at 350 degrees for 15 minutes.
Remove the pie and put into the refreigerator to cool for 2 hours.
Add a layer of whipped cream on top and decorate with the remaining sliced bananas.