And a medium pan, combine sugar, flour, and salt. Mix the milk and the egg yolks together, gradually stir into medium pot with the sugar, flour and salt. Cook and stir over medium heat until thick ( should stick to the spoon). Once thick remove from the heat, add butter and vanilla. Add as much or little coconut as you prefer. Stir to help cook it down for approximately 5-10 minutes. Add to cooked pie shells (should fit in 1 big shell or 2 smaller shells (tart shells can be used) depending on if you want a thin or thick pie. Optional top with whip cream and toasted coconut.