1. For pastry, combine flour and salt in large bowl. Add the 1/4 cup butter and the shortening; toss to coat with flour. Cut in butter and shortening until mixture is crumbly, but with some small pieces of butter remaining. Add ice water, 1 tablespoon at a time, over flour mixture, tossing with a fork, just until pastry begins to hold together. Shape pastry into a disk. Wrap and refrigerate 1 hour or overnight.
2. Adjust oven rack to lower third of oven. Heat oven to 425 degrees F. On a floured surface, roll out pastry with a floured rolling pin to a 13-inch circle. Fit pastry into a 9-inch pie plate, gently pressing pastry along bottom and side of pie plate. Trim edge and flute.
3. Line pie shell with foil. Fill with dried beans or rice. Bake 12 to 14 minutes, until edge of crust is set and lightly colored. Remove foil and beans. Bake crust 10 to 12 minutes, until bottom and sides are golden brown. Cool completely on wire rack.
4. For filling, heat milk, 1/2 cup of the cup coconut, and the vanilla bean (if using) in medium saucepan until hot. Remove pan from heat, cover and let stand 30 minutes. Strain milk mixture through a sieve set over a bowl, pressing on coconut to extract milk; discard coconut. Scrape seeds from vanilla bean, if using, into milk mixture. Whisk together sugar, cornstarch, and salt in a 2-quart heavy-bottomed saucepan. Whisk in yolks until smooth. Gradually whisk in milk mixture. Bring mixture to boil, whisking constantly, over medium heat. Boil 1 minute, whisking gently. Remove from heat; add 1 cup of the remaining coconut, the 2 tablespoons butter, and 2 teaspoons vanilla extract, if using, stirring until butter melts. Pour filling into a medium bowl; place plastic wrap directly against surface and cool at room temperature, 30 minutes.
5. Meanwhile, reduce oven temperature to 325 degrees F. Spread remaining coconut on a large cookie sheet. Bake 6 to 8 minutes, stirring once, until toasted; cool.
6. Sprinkle crust with 1/3 cup of the toasted coconut. Pour filling into crust; spread evenly. Place plastic wrap loosely over pie and refrigerate 3 hours.
7. For topping, measure cream. Transfer 2 tablespoons of the cream to a small microwave proof bowl. Add chocolate and microwave on High 30 seconds. Stir until mixture is smooth (if chocolate does not melt completely, microwave 10 seconds more). Cool at room temperature 15 minutes. Beat remaining cream and 1/2 teaspoon vanilla in mixer bowl until thickened. Add chocolate mixture and beat just until stiff. Spread topping over filling. Sprinkle with the remaining toasted coconut. Makes 10 servings.