Combine:

2 c. flour
1/2 c. softened butter
2 c. light brown sugar

Blend at medium speed until fine crumbs form.

Stir in:

1 c. chopped nuts

Press 2 3/4 cups into a 13x9 baking pan.

Combine:

Remaining mix
1/2 tsp. salt
1 tsp. baking soda
1 tsp. vanilla
2 tsp. cinnamon
1 c. plain yogurt
1 egg
2 c. apples (very last)

Spoon over crumb base.

Bake 40 to 45 minutes.

Cool, cut into squares.