Combine the coconut milk and regular milk. Place 1 C. of this mixture into a pot, along with ¾ C. of sugar.
Whisk the egg yolks and cornstarch into the remaining milk/coconut milk mixture (the one WITHOUT the sugar) and set aside.
On a medium flame, heat the milk sugar mixture until it just starts to boil.
Remove the milk sugar mixture from the heat. With a heatproof measuring cup, scoop out ¼ C of the milk sugar mixture, and temper it into the egg mixture. This involves drizzling the hot liquid into the egg mixture, while whisking the egg mixture vigorously.
Repeat step 4 with another ¼ c. of milk sugar mixture.
While whisking rapidly, slowly pour the egg mixture into the remaining milk and sugar mixture.
On a medium flame, heat the custard until it begins to boil and becomes thick. It may take a few minutes to become thick, but when it does you’ll know it’s done when the thickness doesn’t seem to change anymore.
Remove the custard from the heat and add the vanilla, coconut extract, and butter. Mix until the butter is melted.
Mix 1 C of coconut flakes.
Pour the custard into the baked pie shell, cover with plastic wrap directly touching the top of the custard, and refrigerate for 2 hours.
After the custard has chilled and set, pour the heavy cream into a mixing bowl and beat until soft peaks form.
Add confectioner’s sugar and continue beating until stiff peaks form.
Spread the whipped cream onto the custard, and sprinkle with the remaining shredded coconut.