Beat softened butter until creamy and smooth.Add powdered sugar and mix until light and fluffy.Stir in vanilla extract or rose water and salt.Gradually mix in flour and cornstarch until a soft dough forms.Shape dough into small balls or crescents and place on a baking tray.Press a nut gently into the center of each cookie.Chill shaped cookies for 15 to 20 minutes.Bake at 300°F for 15 to 20 minutes until bottoms are lightly golden.Cool completely before serving.