My Great-Aunt Mary makes this shortbread by hand every christmas, and it is the lightest, butteriest, most delicious tasting shortbread I have ever had. Use berry sugar to gain the right cookie texture.
Beat the sugar and butter with a spoon until creamy. In three batches, sift and mix the flour into the sugar-butter mixture. Mix well, until fluffy. (my Aunt Mary uses a wooden spoon for mixing, but you can use electric beaters).
Pat the dough flat onto a greased cookie sheet, covering about 3/4 of the pan (I pat the dough into neatly formed rectangular shape). Puncture the dough at regular intervals with a fork. Refrigerate for at least 2 hours.
Cut into 15 pieces per pan (1 inch wide). Bake 1/2 hour at 300-325°F Let cool.