01 - Wrap grated raw potatoes in a clean kitchen towel and squeeze firmly to extract excess moisture until potatoes feel dry to the touch.
02 - Mix squeezed raw potatoes with cooled mashed potatoes in a large mixing bowl until evenly distributed.
03 - Sprinkle flour, baking powder, salt, and black pepper over potato mixture. Stir thoroughly to incorporate all dry ingredients.
04 - Gradually pour in milk while stirring continuously to create a thick, slightly lumpy batter that holds its shape when dropped from a spoon.
05 - Melt 1 tablespoon butter with 1 tablespoon vegetable oil in a large nonstick skillet over medium heat until butter foams slightly.
06 - Drop heaping spoonfuls of batter into hot pan, using back of spoon to gently flatten each portion into 1/2-inch thick rounds. Do not overcrowd the pan.
07 - Fry pancakes for 3 to 4 minutes per side until deep golden brown and crispy edges form. Add remaining butter and oil between batches as needed.
08 - Transfer cooked pancakes to paper towel-lined plate to drain briefly, about 30 seconds per side.
09 - Plate pancakes hot, topping each with a generous dollop of sour cream and sprinkle fresh chives over the top.