I love shortbread and I like sugar cookies but a cookie that is both...that's heaven! This is the kind of icing that "dries" and makes almost like a candy shell on the cookie. When the icing is dry, store in an airtight container for up to a week. You can also keep the unbaked dough in the fridge for up to a week...but who can resist making these that long? You have to use butter to get the right taste. Sometimes just for a different flavor I add a teaspoon or two of almond extract.