Leftovers are delicious reheated with butter and seasoned salt, but you can use them in other recipes as well. You can stir small amounts into soup as a thickener. Form the potatoes into patties, dip in flour or seasoned bread crumbs, and fry in oil until crisp. Top a savory meat and gravy filling with mashed potatoes for a Shepherd's Pie. Stir them into a favorite bread dough, like this one.