01 - Place the finely grated raw potatoes into a clean kitchen towel and firmly wring out as much excess moisture as possible to ensure crispness.
02 - In a large mixing bowl, thoroughly combine the moisture-extracted grated potatoes, prepared mashed potatoes, all-purpose flour, baking powder, salt, and ground black pepper.
03 - Gradually incorporate the whole milk and lightly beaten egg into the potato mixture, stirring until a thick, uniform batter is formed.
04 - Heat 1 tablespoon of unsalted butter and 1 tablespoon of vegetable oil in a large nonstick skillet over medium heat until the fats are shimmering.
05 - Working in manageable batches to avoid overcrowding the pan, drop heaping tablespoons of the batter into the heated skillet. Gently flatten each portion slightly with the back of a spoon to form round pancakes.
06 - Cook each boxty pancake for 3–4 minutes per side, or until a deep golden brown and crispy crust is achieved. Replenish butter and oil as necessary for subsequent batches to maintain consistent frying conditions.
07 - Transfer the freshly cooked boxty pancakes to a plate lined with paper towels to absorb any excess oil. Serve immediately while hot for optimal texture and flavor.