Cream the butter and sugar, then add the rest of the cookie ingredients and mix well. It will be a thick dough. Roll the dough into small balls, the place on a cookie sheet. Use a glass to flatten the cookies, then bake at 350 degrees for 10-12 minutes, or until the tops start to crack. Edges could be slightly browned, but they won't necessarily be. Let cool completely before frosting.

To make the frosting, beat the butter, lime juice, lime zest, and dash of salt until creamy, then add the powdered sugar and mix well. Add the milk a little at a time until you get a smooth and creamy consistency. Frost cooled cookies, and sprinkle with lime zest.