This recipe calls for russet, or baking, potatoes. They're a dry, variety that mashes well. Other, waxier types, can turn gluey when mashed. You can use leftover mashed potatoes for this, but if you're cooking the potatoes just for this recipe, use 1 pound. Peel them, then cut them into chunks and boil until soft. Drain very well, and mash until smooth. For variety, you can mix in 1 ½ cups finely chopped broccoli when you add in the garlic and scallions. You can make and coat the patties up to a day in advance, storing them on a plate, tightly covered with plastic wrap, in the refrigerator.