01 - Wrap grated raw potatoes in a clean tea towel and squeeze firmly to remove excess moisture until potatoes feel dry to the touch.
02 - In a large mixing bowl, combine the squeezed raw potatoes with the mashed cooked potatoes, stirring until evenly incorporated.
03 - Add flour, baking powder, salt, and black pepper to the potato mixture. Mix thoroughly until no dry pockets remain.
04 - Gradually pour in milk while stirring, creating a thick batter with a slightly lumpy consistency. Let rest for 5 minutes to hydrate.
05 - In a large nonstick skillet, heat 1 tablespoon butter and 1 tablespoon oil over medium heat until butter melts and begins to shimmer.
06 - Drop large spoonfuls of batter into the hot pan, using the back of the spoon to gently flatten each to about 1/2-inch thickness.
07 - Fry for 3 to 4 minutes per side until deep golden brown and crisp. Flip carefully when the edges appear set and golden.
08 - Transfer cooked pancakes to paper towels briefly to absorb excess oil. Serve immediately with sour cream and fresh chives.