Let cookies cool on baking sheets for 5 minutes before removing to finish cooling on a wire rack. While cookies are cooling, prepare frosting: Beat 3 cups powdered sugar, butter, 9 teaspoons evaporated milk, and vanilla in a bowl until smooth. Gradually stir in remaining 6 cups powdered sugar into mixture until combined.
Now, dig in! Old-fashioned butter cookies are great for all occasions. On their own, they are a good dessert, but you could serve them with coffee or tea for dipping, too. In a large bowl, add the softened butter and sugar, and cream them together until the mixture is light and fluffy.
Simply plop the dough onto a nonstick baking sheet. Then, place the baking sheets in the fridge, and let them chill for at least 30 minutes. "Chilling lets the dough keep its shape when it is baked. If you don't chill the dough first, then the cookies will spread a lot when they bake," Morone says.