Divide the mashed potatoes into 8 equal portions. Use your hands to form 1/2-inch thick patties.

Heat the oil with the butter in a large nonstick skillet over medium-high heat until almost smoking. Mix the flour with the salt and pepper in a pie plate. Coat the potato patties in the flour mixture. Add the potato cakes to the pan and reduce the heat to medium-low. Cook until they have formed a golden crust, 15 to 20 minutes. (Peek underneath using a spatula before turning.) Turn and cook the other side until golden brown, about 15 minutes. Season with additional salt and pepper and serve hot.

Note: Make mashed potatoes from the "innards" of the Garlic Roasted Potato Skins by mashing them with 1/2 cup hot milk and 4 tablespoons of softened, unsalted butter. Don't forget to season them with salt and pepper! Chill the mashed potatoes overnight for the best results.