Sour Cream Lemon Pie

1 cup sugar
3 tablespoons cornstarch
1 cup milk
3 egg yolks, beaten
1/4 cup butter
1-2 tablespoons lemon zest
1/4-1/2 cup fresh lemon juice (juice of 1-2 lemons)
1 cup reduced fat sour cream
1 baked pie crust (9 inch)
1 cup whipping cream (optional)
1/4 cup powdered sugar (optional)
fresh mint leaves, for garnish

Combine sugar, cornstarch, milk and beaten egg yolks in heavy saucepan. Cook and stir over medium heat until thick and bubbly. Remove from heat. Stir in butter, lemon juice and zest. Cool to room temperature (cool quickly by placing pan in a larger pan of ice water and stir frequently). Fold in sour cream. Pour filling into baked pie shell. Cover and refrigerate until firm. Whip cream with powder sugar until stiff peaks form. Place a dollop of whipped cream on each slice of pie. Garnish with a fresh mint leaf. Serves 8.