Combine 1/2 cup sugar and cornstarch in a heavy saucepan; gradually whisk in half-and-half and egg yolks. Bring to a boil over medium heat, whisking constantly; boil 1 minute. Remove from heat.
Stir in butter, coconut, and 1 teaspoon vanilla. Cover tightly with plastic wrap, and cool to room temperature. Spoon custard mixture into pastry shell, and chill 30 minutes or until set.
Beat whipping cream at high speed with an electric mixer until foamy; gradually add remaining1/4 cup sugar and remaining 1 teaspoon vanilla, beating until soft peaks form. Spread or pipe whipped cream over pie. Garnish, if desired.