I cobbled together a few recipes, a little of this and a little of that, and ended up with something pretty good!!
3 cups leftover mashed potatoes
1 cup cheddar cheese, shredded (I used a Cheddar-Jack mix)
salt and pepper to taste (about a teaspoon of each)
1 tsp garlic powder
1 cup seasoned bread crumbs
oil for the griddle
I used a 2-burner griddle to make this go faster. This recipe made about 15 potato cakes.
Mix potatoes, egg, cheese and seasonings (not bread crumbs) in a large bowl. Form into patties and dredge in the bread crumbs. They don't have to be completely coated. Fry on a heated, oiled griddle until brown on both sides. Keep warm in the oven until all the cakes are done.
Note: these are even better when you use a good sharp Cheddar. They're not the prettiest side dish in the world, but they're very tasty.