01 - Wrap the grated raw potatoes in a clean kitchen towel and squeeze firmly to extract as much liquid as possible. This step is crucial for achieving crispy pancakes.
02 - In a large mixing bowl, combine the squeezed grated potatoes, mashed potatoes, flour, baking powder, salt, and black pepper. Mix thoroughly until evenly distributed.
03 - Pour in the beaten egg and milk. Stir until a thick, cohesive batter forms. The consistency should be sticky but manageable.
04 - In a large nonstick skillet, heat 1 tablespoon butter and 1 tablespoon vegetable oil over medium heat until the butter foams slightly.
05 - Drop approximately 1/4 cup of batter per pancake into the skillet. Gently flatten each with a spatula to form even discs. Cook for 3 to 4 minutes per side until deep golden brown and crispy. Add remaining butter and oil as needed between batches.
06 - Transfer cooked boxty to paper towels to drain excess oil. Keep warm in a low oven while cooking remaining batches.
07 - Arrange hot boxty on a serving platter. Top generously with sour cream and sprinkle with fresh chives. Serve immediately while crispy.