Add flour, salt and sugar to a food processor. Pulse to combine.
Add butter cubes, and pulse until the largest pieces of butter are about the size of a pea.
Add the cold water, and pulse until the dough comes together. It should not be wet or sticky.
Shape into a disc, wrap in plastic wrap and refrigerate for at least 1 hour (can be refrigerated up to several days).
To bake, preheat oven to 425 degrees. Roll out pastry on a piece of wax paper so that it is a couple inches larger than a 9" pie plate. Place into the pie plate, and fold edges over and pinch together so that the top edge is thick (this helps to prevent overcooking while the bottom bakes).
Prick the bottom and the sides with a fork, then place a piece of parchment paper inside the crust and will with pie weights or dried beans (this step is optional -- see notes above). Bake for 10 minutes or until top edge is light golden brown.
Remove pie weights and parchment, and bake until bottom crust is light golden brown, about 8-10 minutes. Let cool on a wire rack.
Banana Cream Pie Filling
In a medium saucepan, whisk together half and half, sugar, corn starch and eggs until very smooth.
Place over medium heat, and cook until very thick, whisking constantly. This can take up to 15 minutes -- be patient! You need to heat the filling gradually, stirring constantly, so that it doesn't become lumpy.
Remove from the heat. OPTIONAL: you can strain it through a fine mesh sieve if you notice any lumps.
Stir in peanut butter (if using) and vanilla. Stir in sliced bananas and pour into prepared pie crust.
Cover and refrigerate until chilled and set, at least 4 hours or overnight. Top with whipped cream and serve.
*To make pie crust by hand, stir together flour, salt and sugar. Cut in cold butter with a pastry cutter until about the size of peas. Add cold water and stir until a dough comes together.