Shortbread is an oft abused biscuit. People have added milk, eggs, water, extracts, vegetable oils, and other ingredients that should never appear in these crumbly "cookies".
They are made with only four ingredients, each as fresh as possible. Old butter leaves a metallic tang in the mouth, and old or cheap flour tastes mealy.
Only fresh unsalted butter, unbleached pastry flour, sea salt, and fine sugar will do.
3 cups finely sifted pastry flour
1 cup fine cane sugar
1 cup (2 sticks) of fresh unsalted butter
1 tsp sea salt (pink of grey)
Sift the dry ingredients then blend in the butter, 1 tbls pat at a time. The mix should be soft and granular like sand.
Press into two buttered pie pans. Score mid-way and bake at 350* for 30 minutes.
Set out and re-cut score marks with a large sharp knife. Completely cool. Serve with very hot tea, milky Earl Grey is my favorite.