01 - Place chopped potatoes in saucepan, cover with cold water, add pinch of salt. Bring to boil, reduce heat, simmer until fork-tender (12–15 minutes). Drain and mash until smooth. Let cool slightly.
02 - Squeeze excess moisture from grated potatoes using clean kitchen towel or cheesecloth.
03 - Combine mashed and grated potatoes in large bowl. Add milk, melted butter, scallions, flour, baking powder, salt, and black pepper. Stir until just combined; do not overmix.
04 - Heat large nonstick skillet or griddle over medium heat and add little butter.
05 - Drop heaping spoonfuls batter (about ¼ cup each) onto skillet, gently flattening each to about ½ inch thick.
06 - Cook for 3–4 minutes per side until golden brown and crisp. Work in batches, adding more butter as needed.
07 - Transfer cooked boxty to plate lined with paper towels. Serve warm, garnished with extra scallions if desired.