In a medium saucepan, combine half-n-half, eggs, sugar, flour and salt.
Mix well and bring to a boil over LOW to Meduim low heat. STIR CONSTANTLY, burnt milk is very hard to clean up. You know it is boiling when it continues to have big bubbles even when you are stirring it. (hint: the flour in the mixture will continue to look lumpy until it boils, the constant stirring will break it up and by the time it boils it will incorporate well).
Remove custard from heat and fold in the vanilla and 3/4 cups of the toasted coconut, reserving 1/4 cup of toasted coconut to top the pie when it is ready to serve.
Pour pie filling into the prepared, baked, cooled pie shell and chill until firm — about 4 hours. (hint: don’t put the whipped topping on yet because it will turn to milk as it melts over the hot custard).
When ready to serve, top with whipped topping and sprinkle with reserved toasted coconut.