In a large mixing bowl, combine your leftover mashed potatoes, one egg, shredded cheddar, grated Parmesan, all-purpose flour, chopped green onions, salt, and pepper. Stir until it forms a thick, cohesive batter.

Place a non-stick skillet over medium heat and add butter or oil, allowing it to melt completely.

Using a ¼ cup measuring cup, scoop portions of potato mixture and shape them into flat pancakes.

Cook the pancakes for 3 to 4 minutes on one side until golden, then flip and cook for an additional 3 to 4 minutes.

Once cooked, transfer pancakes to a plate lined with paper towels to absorb excess oil and serve warm with your favorite toppings.