Whisk 1/2 cup sugar, eggs, egg yolk, and flour in medium bowl. Bring milk and coconut to simmer in heavy bottomed medium saucepan over medium heat. Stir occasionally to prevent sticking or burning. Gradually add hot milk mixture to egg mixture, whisking constantly. Return mixture to saucepan; cook until pastry cream thickens and comes to a boil, stirring constantly. Remove from heat. Mix in coconut extract. Transfer pastry cream to medium bowl. Press plastic wrap directly onto surface to prevent formation of skin. Refrigerate until cold, at least 2 hours and up to 1 day. Spoon filling into pre-baked pie crust. Cover with plastic wrap or topping.