Spread the shredded coconut on a baking sheet and toast at 350°F for 5-8 minutes, stirring halfway, until golden. Have your baked pie crust ready and cooled.
In a saucepan off the heat, whisk the sugar, cornstarch, and salt, then slowly whisk in the coconut milk followed by the whole milk until completely smooth with no lumps.
Cook over medium heat, whisking constantly, for 6-9 minutes until the mixture comes to a boil, then keep whisking for 1-2 minutes more until it is a very thick pudding.
Remove from the heat and stir in the butter, vanilla, and 3/4 cup of the toasted coconut.
Pour the hot filling into the crust, press plastic wrap directly onto the surface, and chill for 4-6 hours until fully set.
Whip the cold cream with the powdered sugar to medium-stiff peaks, spread over the pie, sprinkle with the remaining toasted coconut, and slice.
