When I was growing up my mom would make potato cakes with our Sunday leftover mashed potatoes. It was one of my favorite comfort foods and I find myself wanting to make mashed potatoes for dinner just so I can make potato cakes the next morning. They're so easy and really tasty. I love to eat it with lots of ketchup on top and a steamed egg with a slice of my mom's homemade wheat bread toasted with honey. Makes such a yummy breakfast.
There's not really a recipe for this but here's the general idea. You can, of course, doctor these up any way you like. You could add some green chilies and maybe some chili powder and serve it with salsa to make it more Mexican but I like it this way.
Stir the mashed potatoes together until smooth again. Mix in egg until well blended. Then stir in cheese and salt and pepper. Heat a skillet over medium high heat. Melt a Tablespoon of butter on skillet and plop (very technical term, you know) about 1/2 cup of potato mixture onto skillet. Spread it out a bit until it makes a nice "cake". Let cook about 3 - 5 minutes until a nice brown crust forms on the bottom. Flip over and cook another 3 - 5 minutes on the other side. Repeat with remaining potato mixture. Serve with ketchup.