1 3/4 c. flour
1/4 c. sugar
1 tsp. cinnamon
1/2 tsp. salt
2/3 c. (1 1/3 sticks) butter
3 tbsp. water, or more if necessary, to bind dough

FILLING:

1 1/2 c. sour cream
1 lg. egg
1 c. sugar
1/4 c. flour
2 tsp. vanilla
1/2 tsp. salt
2 1/2 lbs. apples (6-9 sm.), pared, cored, and sliced

TOPPING:

1/2 c. (1 stick) butter
1/2 c. flour
1/3 c. sugar
1/3 c. brown sugar
1 tbsp. cinnamon
1/4 tsp. salt
1 c. chopped walnuts

Preheat oven to 450 degrees.

To prepare crust: Combine flour, sugar, cinnamon, and salt. Cut in butter to a consistency of coarse meal. Add enough water to moisten. Roll out on lightly floured board. Turn pastry into 10-inch pie plate. If you prefer, prepare pastry in food processor.

To prepare filling: Combine sour cream, egg, sugar, flour, vanilla, and salt in a large bowl. Add sliced apples to mixture, stirring to coat. Pour filling mixture into pie shell, just before placing into oven. Bake 10 minutes. Reduce heat to 350 degrees and bake for 35-40 minutes.

Meanwhile, prepare topping: Blend together butter, flour, sugar, brown sugar, cinnamon, salt, and walnuts.