Preheat the oven to 375. Butter a 9” or 10” inch pie dish and line with the pie crust. Using a fork poke a few holes in the bottom. Line the crust with first a scrunched up piece of baking parchment smoothed out again so it sits with the curve of the crust, then with baking beans.
Bake for 20-30 minutes (this will depend on your oven temperature and if you’re making the crust from scratch or using store bought) until the crust is just golden and cooked through both around the edges and in the middle. Remove the baking parchment and baking beans, and set aside to cool completely.
While the oven is still hot, spread the shredded coconut for both the pie and the topping across a large baking sheet and toast for 3-4 minutes, tossing once, until the coconut is just golden. Remove from the pan and set aside to cool.
Once the crust is cool, start the cream pie filling. In a large saucepan whisk together the egg yolks, milk, heavy cream, sugar, cornstarch and salt. Once the mixture is smooth set over a medium heat. Bring the mixture just to the boil, stirring constantly. Reduce the heat to medium low and whisk for another 2 minutes before removing it from the heat.
Whisk in the 1 cup of toasted coconut along with the vanilla and the coconut rum, if using.
Pour into the prepared pie crust. If you have a little filling leftover only take it to the top of the crust; this will depend on your pie dish or crust. Chill for at least 4 hours, or overnight.
Up to an hour before serving, gently whip the heavy cream with the powdered sugar and vanilla until it just holds it’s shape. Using a spatula spoon the cream on top of the pie before scattering it with the remaining toasted coconut.