In a medium bowl, combine the sifted powdered sugar and milk.
Add the vanilla extract and almond extract if using.
Whisk the mixture until smooth and glossy, ensuring there are no lumps.
Adjust the consistency by adding more milk, a few drops at a time, if the icing is too thick, or more powdered sugar if too thin.
Use immediately to ice cooled shortbread cookies, spreading or piping as desired.
Allow the icing to set at room temperature for about 30 minutes before serving or storing.