Amish sour cream apple pie

1 c  Sour cream
      1 lg Egg
    3/4 c  Sugar
      2 tb All-purpose flour
    1/4 ts Salt
      1 ts vanilla extract
  2 1/2 c  Apples, peeled; diced
      1    9 inch pie shell; unbaked
           Crumb topping:
    1/2 c  Brown sugar, packed
    1/3 c  All-purpose flour
    1/4 c  butter
      1 ts Ground cinnamon
 
  Recipe by: Jo Merrill Use dairy sour cream for this recipe-not a sour cream
  substitute.
      Beat sour cream and egg together; add sugar, flour, salt and vanilla.
      Mix until smooth.  Stir in apples. Place mixture into pie shell and bak
      in preheated 400 degree oven for 25 minutes.
      Meanwhile mix topping ingredients until crumbly-- Remove pie from oven
      and sprinkle the crumb topping over. Bake 20 minutes longer.
 
-----