01 - Place the grated raw potatoes in a clean kitchen towel and squeeze out as much liquid as possible.
02 - In a large bowl, combine the grated potatoes, mashed potatoes, and scallions.
03 - In a separate bowl, whisk together the flour, baking powder, salt, and pepper.
04 - Add the dry ingredients to the potato mixture and mix gently.
05 - In another bowl, whisk the milk, egg, and melted butter. Pour this into the potato mixture and stir until just combined — do not overmix.
06 - Heat a large skillet or griddle over medium heat and add a thin layer of butter.
07 - Drop heaping spoonfuls of the batter onto the skillet, flattening each to about 1/2 inch thick.
08 - Cook for 3–4 minutes per side, until golden brown and crisp. Work in batches, adding more butter as needed.
09 - Transfer cooked pancakes to a paper towel-lined plate. Serve hot, garnished with sour cream and chives if desired.