For the simple syrup: In a saucepan, combine water and sugar over medium heat. Bring to a boil, reduce heat and simmer for 5 minutes, stirring occasionally, until the sugar has dissolved. Take pan off heat and cool the syrup. Any extra cooled syrup can be stored in an airtight container in the refrigerator for up one month.
Mix the milk and cream in a 20 by 33cm glass baking pan and put it in the freezer for 2-3 hours. Every 30 minutes, scrape the ice that forms with a fork to create a soft, icy mixture. The icy mixture can be made one day ahead, stored in the freezer covered with cling film.
In a blender, combine the icy milk-and-cream mixture with the espresso and simple syrup. Blend until smooth. Spoon into decorative serving glasses and top with the crumbled cookies.