Mix flour, sugar, salt and baking soda
Dice butter and work into dry ingredients with finger tips until you have pea size pieces
Mix egg and vanilla, add to bowl with part of sour cream cut into mix with a butter knife
Add rest of sour cream, mix with knife - don't over mix
Let stand in 1 hr. in refrigerator or overnight
Roll out on lightly floured Pastry Cloth, cut and sprinkle with sugar
Bake 400°F for 15 minutes *Oven times may vary - Loma finds 15 minutes to be too long - I cook about 11-12 minutes