Fit 1 piecrust into a 9-inch pie plate according to package directions; fold edges under, and crimp. Prick bottom and sides of piecrust with a fork. Bake according to package directions for a one-crust pie.
Combine 1/2 cup sugar and cornstarch in a heavy saucepan. Whisk together half-and-half and egg yolks. Gradually whisk egg mixture into sugar mixture; bring to a boil over medium heat, whisking constantly. Boil 1 minute; remove from heat.
Stir in butter, 1 cup coconut, and 1 teaspoon vanilla. Cover with plastic wrap, placing plastic wrap directly on filling in pan; let stand 30 minutes. Spoon custard mixture into prepared crust, cover and chill 30 minutes or until set.
Beat whipping cream at high speed with an electric mixer until foamy; gradually add 1/3 cup sugar and remaining 1 1/2 teaspoons vanilla, beating until soft peaks form. Spread or pipe whipped cream over pie filling. Garnish, if desired.