1 (9") deep dish pastry shell
1 c. sour cream
1 egg, lightly beaten
2 tsp. vanilla
3/4 c. sugar
1/8 tsp. salt
1/4 c. flour
2 lbs. Granny smith apples, peeled, cored & thinly sliced

Prepare pastry shell and set aside. Combine sour cream, egg, vanilla, sugar, salt and flour; stir in apples. Pour into unbaked pastry shell. Bake at 425 degrees for 10 minutes. Reduce heat to 350 degrees and bake for 30 minutes. Spoon topping over pie and bake for 15 to 20 minutes or until filling is bubbly.

TOPPING:

1/3 c. flour
1/4 c. sugar
1/4 c. packed light brown sugar
2 1/2 tsp. ground cinnamon
3/4 c. chopped walnuts
6 tbsp. unsalted butter, cut into pieces