01 - Place the grated potatoes in a clean kitchen towel and squeeze out as much liquid as possible. Transfer to a large bowl.
02 - Add the grated onion, sliced scallions, egg, flour, salt, and pepper. Mix well until evenly combined.
03 - Heat 2 tablespoons of vegetable oil in a large nonstick skillet over medium heat.
04 - Scoop 2–3 tablespoons of the potato mixture for each cake, flattening gently with a spatula to form patties about 1/2 inch thick.
05 - Fry 3–4 cakes at a time for 3–4 minutes per side, or until golden brown and crisp. Add oil as needed between batches.
06 - Transfer cooked cakes to a plate lined with paper towels. Keep warm while cooking remaining cakes.
07 - Serve hot, topped with sour cream and a sprinkle of fresh chives or scallions if desired.