In a saucepan, whisk sugar, cornstarch and salt together. Add in milk and whisk thoroughly. .
Cook over medium heat, stirring constantly, until mixture thickens and boils. Boil for 1 minute. Remove from heat.
In a separate bowl, whisk egg yolks while slowly pouring most of the hot milk mixture into the eggs,.
Return mixture to the saucepan, bring to a boil and boil for one more minute, stirring constantly, Remove from heat.
Add butter and vanilla. Stir until completely melted.
Add coconut, stir together and pour into a baked pie shell.
Let cool for about 20 minute Put a piece of waxed paper over the top (to keep the pie from drying out) and put in the fridge until is is completely chilled.
In a bowl, add whipping cream and powdered sugar. Beat with a mixer until thick.
Remove waxed paper from pie, top with the whipped cream, and garnish with toasted coconut.