Crescent or round-shaped buttery shortbread cookies, often using ground almonds in place of the flour, and covered in powdered sugar. Some are flavoured with brandy or mastic liqueur; often the centre is pierced by a whole clove. They are served at the Christmas holidays or for weddings, when it's hard not to spill the sugar on your fancy clothes.
Curiously, in Turkey they are called Kavala Kurabiyesi, Kavala-style cookies.
Image by Jastrow, Creative Commons License