This is my favorite shortbread recipe. It was handed down to me many years ago. The secret is to make sure it is kneaded for a long time.
1 LB. BUTTER
4 CUPS FLOUR
1 CUP FRUIT (BERRY) SUGAR
4 TBSP. CORNSTARCH
In electric mixer, beat sugar and butter until very smooth. Add cornstarch and flour and mix until mixture begins to clump together.
Remove from mixer and knead until cracks form, (see photo)
Roll out about 1/4 to 1/3 inch thick and cut out. Prick with a fork.