Sift the flour from a height onto a clean work surface and sift the icing sugar over the top. Using your hands, work the cubes of butter into the flour and sugar by rubbing your thumbs against your fingers until you end up with a fine, crumbly mixture. This is the point where you can spike the mixture with interesting flavors, so mix in your lemon zest.
Add the eggs and milk to the mixture and gently work it together until you have a ball of dough. Flour it lightly. Don't work the pastry too much at this stage or it will become elastic and chewy, not crumbly and short. Flour your work surface and place the dough on top. Pat it into a flat round, flour it lightly, wrap it in plastic wrap and put it into the refrigerator to rest for at least half an hour.
