Start with cold mash. If your mashed potatoes are extra creamy or loose, don’t worry — we’ll adjust with flour. If they’re very stiff, let them sit at room temperature for 10 minutes so they’re easier to stir.
Mix the base. In a large bowl, combine the mashed potatoes, egg, flour, cheese (if using), scallions, baking powder, garlic powder, salt, and pepper. Stir with a spatula or wooden spoon. You’re aiming for a mixture that clumps easily and doesn’t stick too much to your hands.
Adjust as needed. If the mixture feels too sticky or spreads when you press it, add flour, 1 tablespoon at a time. If it’s crumbly and dry, splash in a teaspoon of milk or a little melted butter. The right texture holds a neat patty.
Preheat the pan. Set a large nonstick or well-seasoned cast-iron skillet over medium heat. Add 1 tablespoon oil and a small pat of butter, if you like. Give it a minute to get hot. You should hear a gentle sizzle when batter hits the pan, not silence, not a scream.
Shape and cook. Scoop about 1/4 cup of the mixture and gently pat it into a puck, roughly 3 inches wide and 1/2 inch thick. Place it in the pan. Repeat, leaving a little space between them. Pan shouldn’t be overcrowded; better to do two batches than steam them.
Let them get golden. Cook 3 to 4 minutes on the first side, until deeply golden and crisp at the edges. Flip carefully with a thin spatula and cook another 2 to 3 minutes. Adjust the heat if they’re browning too fast before the center heats through. Add more oil as needed between batches.
Keep warm. Transfer finished pancakes to a wire rack set over a sheet pan in a 200°F oven while you finish the rest. The rack keeps them crisp.
Serve right away. Top with a spoonful of sour cream and chives, a runny fried egg, or something sweet like applesauce. They’re friendly like that. A crisp salad on the side is nice, too.