Separate the egg yolks from the egg whites; set the whites aside and reserve for another use. Combine sugar, cornstarch, salt and milk. Cook sugar mixture over medium to low heat stirring constantly. After the mixture bubbles up and thickens, cook an additional 2 minutes. Remove from heat. Beat egg yolks slightly. Gradually stir 1 cup of hot mixture into yolks. Return egg mixture to saucepan; bring to a gentle boil. Cook and stir 2 minutes more. Remove from heat. Add butter and vanilla; stir until butter is melted. Add the coconut and mix. Pour into a baked 9-inch pie crust. Top with whipped cream and toasted coconut. You can use the reserved egg white for meringue, if preferred.