Preheat oven to 350 degrees F.
With a mixer, blend flour, brown sugar and softened butter until crumbly. The consistency should be that of sand; stir in chopped nuts.
Press 2 3/4 cups of the mixture into an ungreased 9x13 inch pan.
To the remaining mixture, add cinnamon, baking soda, salt, sour cream, vanilla and egg; blend well. Stir in apples.
Spoon evenly over the base in pan.
Bake for 25 to 35 minutes or until golden brown, and a toothpick comes out clean.
Cut into squares, and serve with whipped cream if desired.