Preheat oven to 325 degrees F (165 degrees C). Cream butter and brown sugar. Add 3 to 3 3/4 cups flour. Mix well. Sprinkle board with the remaining flour. Knead for 5 minutes, adding enough flour to make a soft dough. Roll to 1/2 inch thickness. Cut into 3x1 inch strips. Prick with fork and place on ungreased baking sheets. Bake at 325 degrees F (165 degrees C) for 20 to 25 minutes.