Demerara sugar is a raw sugar made from sugarcane. It has large granules and hints of molasses, which is why it's perfect for this recipe. Plus, it makes your cookies sparkle! Because the cookies are so soft, the large sugar granules hold up against the higher moisture content in these cookies. It's actually quite easy to find in any grocery store but if you can't find demerara specifically, you can also use raw sugar or even regular sugar.