If you can't find cake flour or bread flour: for cake flour, use 1 cup all-purpose minus 2 tablespoons, plus 2 tablespoons cornstarch. For bread flour, substitute with all-purpose—the cookies will be less chewy but still delicious. For extra flavor, fold in 1 cup toasted walnuts or pecans. Dough freezes beautifully: scoop balls, freeze on a tray, then bag. Bake from frozen with 1–2 extra minutes.