Place top oven rack in the center position and pre-heat oven to 400°F.
Use a stand or hand-held mixer to prepare the pie crust. Add the flour, salt, and shortening in a medium-size bowl and mix to combine.
Add the ice-cold water a little at a time, until the dough clumps together and can form a ball.
On a lightly floured surface, roll out the dough into a 12-inch diameter. Fold the dough in half and then in half again and transfer to a 9-inch diameter deep-dish pie plate. Press the dough down into the pie pan. Trim if there is more than ½ inch of excess dough hanging over the edges. Fold the edges of the dough under, and then crimp together with your thumb or a fork.
Line the pie crust with parchment paper and fill it with pie weights or dry beans. Blind bake (aka “pre-bake”) the crust in the pre-heated oven for 15 minutes.
Remove the crust from the oven and remove the dry beans or pie weights. Set aside.
To make the filling, combine the milk, cream, eggs, sugar, salt, corn starch, and gelatin in a large saucepan. Stir until well blended and heat over medium-low heat while whisking often. When the custard has thickened and becomes difficult to stir, turn the heat off and stir in the butter and vanilla. Set aside.
Slice the bananas and line the bottom of the pie crust with two layers of sliced bananas. Pour the custard over the bananas and smooth the custard out throughout the pie.
Reduce the oven temperature to 350°F and bake for 20-25 minutes.
When the baking time finishes, remove pie from oven and cool completely before transferring to the refrigerator. Chill for a few hours or overnight before serving.
To serve, top with whipped cream and additional banana slices, if desired. Enjoy!