I used leftover mashed potatoes to make these fried potato patties.
1/4 cup Canola Oil
1/4 cup (1/2 stick) Butter
2 cups Cold Mashed Potatoes
Optional add-ins: see note
1/2 cup All-purpose Flour
Salt and pepper
Heat oil and butter in a wide skillet on Medium heat.
Put the flour in a bowl or pie pan.
Combine mashed potatoes with the egg and any add-ins. Scoop out 1/4 cup of the mixture, shape into a patty, and dredge both sides in flour.
Fry for 5 minutes on each side, or until golden brown. Remove to wire rack to drain and season immediately with salt and pepper.
NOTE: Optional add-ins could include any combination of the following: 1/4 cup corn, 2 Tbs. diced onion, 1/2 cup shredded cheese, 2 tsp. dried chives, 2 Tbs. bacon bits, etc.
I added in leftovers that I had on hand - corn and diced onion.