SALTED butter (SEE NOTE 1) • egg yolks • vanilla extract (OPTIONAL) • icing sugar (SEE NOTE 2) • milk powder • plain flour • corn flour (SEE NOTE 4) • custard powder • potato flour (SEE NOTE 4) • . Butter should be at a cool room temperature, so it's soft enough to cream with sugar to create air pockets but still firm enough to prevent cookies from spreading • . Icing sugar is also known as powdered sugar or confectioners' sugar. It creates a soft, tender, melt-in-your-mouth texture cookies • . Sifting all flour together in ✅️B is done to break up lumps, aerate the mixture, and distribute ingredients evenly, resulting in lighter, fluffier baked goods with a more consistent texture •