Preheat oven to 350 degrees F. Have ready a fully baked 9 inch deep dish pie crust.
Put the egg whites in a mixing bowl and have the cream of tartar, sugar and handheld mixer ready so that you can make the meringue quickly and put it on the hot filling.
To make the filling, combine the egg yolks and sugar in a large (3-31/2 quart) saucepan. Gradually add the half & half, then add the cornstarch and stir until well mixed. Put the saucepan over medium heat and bring to a boil, stirring constantly until mixture thickens. Continue to boil and stir for about 1 ½ to 2 minutes. Remove from heat and stir in the butter and vanilla, then add 1 cup of the coconut (save remaining ½ cup for topping). Keep the filling in the pan while you make the meringue.
Working quickly, make the meringue. Beat the egg whites and cream of tartar until they are foamy, then gradually add the sugar and beat until stiff peaks start to form.
Pour the hot filling into pie crust, then spread the meringue on top of the hot filling, sealing the edges. Sprinkle remaining ½ cup coconut on top and bake at 350 for 15 minutes or until meringue is browned. Let cool at room temperature for about an hour, then transfer to the refrigerator for several hours so that pie can chill and firm.
This recipe was loosely adapted from a recipe from the Southwest Texas Dairy Farmers.