Place mashed potatoes, egg, panko and cheese in a large mixing bowl.
Using a fork, break the potatoes apart, then stir everything together, whipping until combined. Add any optional ingredients to the potato mixture, stir again.
With wet hands, form eight, golf-ball-sized balls.
Place ½ cup panko on a plate. Flatten the mashed potato balls into cakes or patties, about ¾ – 1 inch thick, on top of the panko, turning to coat each side.
Heat a generous amount of olive oil in a skillet over medium-low heat. Pan-sear each potato cake, until each side is golden brown. Keep in a warm oven (or toater oven) until ready to serve.
Alternatively, you can spray each side of the potato cake with spray olive oil, and place in a convection oven, toaster oven or air fryer until crisp and golden.
