Preheat oven to 425°.

To make the filling, heat the milk and sugar in a heavy saucepan until just below the boiling point. Remove from the heat. In a small bowl, mix the egg yolks, cornstarch and salt. Pour a small amount of the hot milk into the egg yolk mixture, stirring vigorously, so that the eggs do not curdle. Then add to the milk pan whisking continuously until it is combined. Heat on medium-low until the mixture thickens, alternating between using a whisk and a rubber spatula to stir and scrape the sides of the pan. It is done when the custard heavily coats the back of a spoon. Remove from the heat and stir in the butter until melted. Add the rum and pineapple. Transfer to a shallow bowl and cover with plastic wrap and chill for 1 hour.

While the custard is chilling, roll out each disk of dough and place in an 8-inch pie shell. Line with foil or parchment paper and fill with pie weights or dried beans. Blind-bake for 15 minutes, then reduce oven temperature to 350°. Remove pie weights and bake for an additional 10-15 minutes or until golden. Cool on a rack.

Toast the coconut on a pie tin or baking sheet in the 350° oven for 5-10 minutes or until it is still white, but slightly golden in color.

Prepare the topping by whipping the cream, the vanilla and powdered sugar on high until stiff peaks form. Set aside.

Spoon the chilled pineapple custard filling into the pie shells, making a taller mound in the center. With a rubber spatula place the whipped cream in a piping bag for a professional look or you can spread the cream over the custard starting from the center and rotating the pie pan until the cream is spread over the entire pie without touching the pastry on the sides. Spread the coconut in a light layer along the edge of the pie.

If desired, garnish the pie, by placing 6 maraschino cherries and small pineapple wedges next to the coconut, one set for each slice of pie.

Refrigerate the Pina Colada Pie until served.