When are Potatoes Done? Tips, Terms & Tools Add comments Jun 062006 When boiling potatoes for either mashed or simple boiled, it is key to know when they are cooked all the way through. The easiest way to tell is to stick a knife in the potato. If it does not slide off easily then they need more time. Leave a Reply Cancel reply Name (required) E-mail (required) URI Your Comment You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>