Sour Cream Apple Pie

Vigorously stir sour cream and egg; add flour, sugar, salt, and vanilla. Mix until smooth. Stir in apples. Pour mixture into pie shell. Bake at 400 degrees for 25 minutes. Remove pie from oven. Spread with topping that has been mixed until crumbly. Bake an additional 20 minutes.

Source: The NW Indiana Times - The Amish Cook