Lemon-blueberry cream pie

1 cup sugar
3 tablespoons cornstarch
1 cup milk
3 beaten egg yolks
1/4 cup butter or margarine
1 tablespoon finely shredded lemon peel
1/4 cup lemon juice
1 8-ounce carton dairy sour cream
2 cups fresh blueberries
1 9-inch baked pastry shell
Finely shredded lemon peel (optional)
Sweetened whipped cream (optional)
Lemon slices (optional)

1. In a saucepan combine 1 cup sugar and cornstarch. Add milk, egg yolks, butter or margarine, and 1 tablespoon lemon peel. Cook and stir over medium heat until thickened and bubbly; cook and stir 2 minutes more. Remove from heat; stir in lemon juice. Transfer to a bowl; cover surface with plastic wrap and refrigerate until cool.
2. When cool, stir sour cream and blueberries into mixture; pour into pastry shell. Cover and chill at least 4 hours. If desired, stir a little lemon peel into sweetened whipped cream. Pipe or spoon atop pie. Garnish with lemon slices, if desired.