1 (9 inch) unbaked pie crust
1/4 cup unbleached all-purpose flour
1 cup white sugar
1 teaspoon salt
1/2 teaspoon ground cinnamon
1 cup buttermilk
2 egg whites
1/2 cup shortening
1 cup heavy cream
1 teaspoon vanilla extract
1/2 cup white sugar
1/2 cup chopped pecans (optional)