This recipe, from Cooks Illustrated, was not to have been made public. Unfortunately, late one night I inadvertently hit the wrong button. So credit must be given to the source. Russet potatoes will yield a slightly fluffier, less creamy mash, but they can be used in place of the Yukon Gold potatoes if desired. Rinsing the potatoes in several changes of water reduces starch and prevents the mashed potatoes from becoming gluey. It is important to cut the potatoes and root vegetables into even-sized pieces so they cook at the same rate.