In a medium sauce pan, combine sugar and cornstarch. Add half & half and egg yolks and whisk until well combined. Bring to boil over medium heat, stirring constantly. Boil 1 minute and remove from heat. Stir in butter, coconut and vanilla. Pour into medium bowl, cover with saran wrap directly on the filling itself to avoid a sticky film on top. Let sit to cool. Once completely cool, stir in thawed Cool Whip. Top with toasted coconut and serve with graham crackers, vanilla wafers, or Teddy Grahams.