Before starting the custard, spread all your shredded coconut on a baking sheet. Bake at 325°F for 5–8 minutes, tossing frequently, until golden brown. This removes the "chewy" moisture and adds a macaroon-like crunch.
In a medium saucepan, whisk the sugar, cornstarch, salt, milk, and coconut milk. Cook over medium heat until bubbling. Whisk a half-cup of the hot liquid into the egg yolks in a separate bowl to "temper" them, then pour the yolk mixture back into the pan. This prevents the eggs from scrambling.
Continue cooking for 2 more minutes until the whisk leaves distinct trails in the custard. Remove from heat and stir in the butter, vanilla, coconut extract, and 1 cup of the toasted coconut.
Pour the filling into the pre-baked pie shell. Immediately press a piece of plastic wrap directly onto the surface of the custard. This is essential to prevent a rubbery "skin" from forming as it cools.
Refrigerate for at least 4 hours. A cold custard is a stable custard.
Beat the heavy cream and confectioners' sugar until stiff peaks form. Spread over the chilled pie and top with the remaining toasted coconut and a few extra flakes for visual texture.