1 lb. butter
1/2 c. firmly packed brown sugar
1/2 c. firmly packed powdered sugar
4 c. flour

Soften butter. Cream butter with mixer. Add sugars and mix on slow very well. Add flour; mix thoroughly. Press in 14"x12" pan. Bake at 350 degrees for 20 minutes then at 325 degrees for 20 minutes more. To brown, 5 more minutes. Cut in squares when cool.