1 lb. butter (no substitute)
1 c. sugar
4 c. flour
1/2 c. cornstarch

Combine all ingredients into large bowl. Mix by hand until dough becomes smooth and satiny (if dough is not mixed well, shortbread will be floury). Pat into 13"x9" pan. Bake at 325 degrees (do not preheat oven) for 1 hour and 10 minutes or until surface is light golden brown. Cut into desired shapes.