Combine butter, flour, and salt. Using a pastry blender, cut in the butter until very crumbly. Add chilled water a few tablespoons at a time, mixing with a fork until the dough pulls together. Form into a disk, wrap in plastic wrap, and chill for at least 2 hours up to overnight.
Gently roll the piecrust out to a 12-inch circle on a lightly floured surface. Fold the piecrust or roll it around your rolling pin to move it to the pie plate. Gently tuck it into the pie pan, trim the edge about an inch over the side, tuck the excess in along the edge, and flute it. Refrigerate the crust for several hours.
Preheat oven to 375 degrees. Line the pie crust with aluminum foil and fill it with pie weights, rice, beans, or sugar. Bake for 15 minutes. Remove from the oven and carefully remove the weights and foil. Using a fork, prick holes all over the bottom of the crust. Place back in the oven and bake for an additional 15 minutes or until the bottom is golden brown.
In a medium saucepan, whisk together the sugar, cornstarch, coconut milk, and half and half. Bring to a boil over medium heat and cook for 2 minutes, whisking very frequently. Reduce the heat to low, and in a separate bowl, whisk the egg yolks. Add 2-3 tablespoons of the hot mixture to the 4 eggs yolks whisking until thoroughly incorporated. Repeat the procedure several times until the egg yolks are warmed thoroughly. Slowly whisk the egg yolk mixture into the hot pudding mixture. Increase heat to medium and boil for 2 minutes, whisking constantly.
Remove from the heat and stir in the coconut, butter, and vanilla. Pour into the cooled piecrust and cover with plastic wrap directly over the surface of the pudding. Chill in the fridge for at least 3 hours up to overnight.
Add 1/3 cup coconut to a large skillet over medium-low heat. Cook until mostly golden brown, stirring frequently.
Using a hand mixer or a stand mixer with the whisk attachment on medium-high speed, beat heavy whipping cream and powdered sugar until soft peaks form. Slowly add the cornstarch and vanilla and continue beating until stiff peaks form. Remove the plastic wrap from the refrigerated pie and gently spread or pipe over the top of the pie. Sprinkle with the cooled toasted coconut.