2 c. flour
2 c. light brown sugar, packed
1/2 c. butter, softened
2 c. walnuts, chopped
2 t. cinnamon
1 t. baking soda
1/2 tsp. sea salt
1 c. sour cream
2 t. vanilla extract
1 egg
2 1/2 c. finely chopped, firm apples

Combine flour, brown sugar, and butter in a large mixing bowl. Blend on low speed until fine crumbs form. Add walnuts.
Press 3 cups of crumbs into a buttered 9-by-13-inch baking pan.
To remaining crumbs add cinnamon, baking soda, salt, sour cream, vanilla and egg and blend well. Fold in apples and spread evenly over crumb base.
Bake in preheated 350 degree oven for 35-40 minutes or until toothpick comes out clean.
Sprinkle generously with powdered sugar.