Chop the Coconut - Add 1/2 cup of coconut flakes to a blender or food processor. Process until ground into smaller pieces for the pie crust. Alternatively, chop it into tiny pieces. Set aside.
Make the Pie Crust - In a medium bowl, whisk the flour, salt, and ground coconut flakes. Add the cold pieces of butter and shortening to the flour, tossing to coat. Use your fingers or a pastry cutter to cut the shortening and butter into the flour mixture until it resembles a coarse meal with some pea-sized pieces remaining. Gradually stir in the water with a fork until the dough just comes together.
Rest the Dough - Scrape the dough onto a work surface, lightly knead, and gather up any crumbs. Then, form the dough into a 6-inch round disk. Wrap in plastic and refrigerate until chilled, about 1 hour.
Shape the Pie Crust - On a lightly floured work surface, roll out the dough to a 12-inch round, about ¼-inch thick. Ease the dough into a deep 9-inch glass pie plate. Trim the overhanging dough to 1 inch and fold it under itself. Decorate the edges as desired and chill the crust until firm, about 15 minutes.
Heat the Oven - PreHeat the oven to 375°F (191ºC).
Par-Bake the Crust - Place the pie plate on a sheet pan. Line the crust with parchment paper and fill with pie weights or dried beans. Cover the edges with strips of foil and bake in the lower third of the oven for 20 minutes until the crust is barely set.Remove the parchment and pie weights and bake with the foil on the edges for 5 minutes until the crust is set but not brown. If the bottom of the crust is puffed up, lightly poke it a few times to deflate. Let the crust cool for 10 minutes on the sheet pan, leaving the foil strips on the edges.
Make the Custard Filling - In a medium bowl, whisk the sugar and melted butter. Whisk in eggs until smooth. Add the buttermilk, vanilla and salt, whisking until incorporated. Stir in the coconut. Pour the filling into the pie crust.
Bake - Lower the oven temperature to 350°F (177ºC). Bake on the middle rack for 45 to 55 minutes, until the custard is set and golden brown on top. Remove the foil after 40 minutes. If the crust starts to brown too quickly, add foil back on the edges.
Cool and Serve - Carefully transfer the pie to a cooling rack. Let it cool completely. Slice and serve with ice cream or whipped cream.
Notes
Storing: The pie can be covered and refrigerated for up to 5 days.
Reheating: Warm in the oven at 300ºF (149ºC) until the filling and crust are warm.
Serving Suggestions: The pie is best served with coconut or vanilla ice cream.