Syrups made with fresh blueberries, strawberries, and mint make these pastel icings look as good as they taste. Simply stir confectioners' sugar into syrup to reach the consistency of honey. Then dip cupcake tops into icing, or pipe it onto sugar cookies.
The icing can be prepared up to two days in advance; refrigerate it in an airtight container with a damp towel or plastic wrap on the surface. Cupcakes and cookies can be iced up to a day ahead.