Combine sugar, cornstarch and salt in a heavy saucepan, stir well.
Combine coconut milk and enough milk to make 3 cups.
Mix egg yolks and milk mixture and stir into sugar mixture. Cook on medium heat until mixture thickens, then boil for 1 minute; stirring constantly; remove from heat.
Add butter, vanilla and coconut. Cool for 30 minutes.
Pour cooled pudding mixture into prepared pie crust. Cover with plastic wrap and refrigerate for at least 2 hours.
For toasted coconut, preheat oven to 400 degrees F. Spread coconut on baking sheet. Watch carefully as it burns easily. Stirring every minute, bake for 4-5 minutes until toasted to golden brown; cool.
Beat whipping cream and powdered sugar together until soft peaks form. Spread over cake and top with toasted coconut.