Add the ingredients for the potato cakes (minus the flaky salt for finishing) to a bowl and mix. If your leftover mashed potatoes aren’t seasoned, add a pinch or two of sea salt or table salt and pepper.

Make the flour mixture by mixing flour, salt, and pepper in a separate shallow dish.

Scoop out 3 to 4 tbsp of the mashed potato and leftovers mixture, coat it in the flour mixture (shaking off any excess flour), and form it into a round, flat patty about 3 inches wide and ¾ inch thick. Finish making patties with the rest of the leftover mixture.

Heat 2 to 3 tbsp oil in a pan over medium to medium-high heat. Once the oil is hot, place 5 to 6 patties in the pan and cook for 3 to 5 min or until the bottoms are golden brown. Flip the cakes over, cook for 3 to 5 min more or until golden, then remove from the pan and place on a wire rack to cool (this will help them stay crispy on the outside too). Repeat until all the mashed potato cakes are made (adding more oil to the pan if needed).

Sprinkle the potato cakes with flaky salt (like Maldon) or a pinch of regular table salt while they're still warm.

Top the mashed potato cakes with sour cream, cranberry sauce, and green onions (optional).