01 - Place diced potatoes in a large pot and cover with cold water. Bring to a boil over medium-high heat, add a pinch of salt, and cook for 12–15 minutes until fork-tender.
02 - Drain potatoes well and return to the hot pot for 1–2 minutes to steam dry, removing excess moisture.
03 - Mash potatoes thoroughly until smooth and lump-free.
04 - While potatoes are still warm, add 3 ½ tbsp butter and mash until melted and fully incorporated.
05 - Stir in flour, salt, and black pepper. Mix with a wooden spoon, then knead briefly by hand in the bowl until a soft but not sticky dough forms. Add additional flour if needed.
06 - Turn dough onto a lightly floured surface. Pat or roll out to a round about ½ inch thick. Cut the round into quarters to make four triangular farls. For smaller farls, cut each quarter in half.
07 - Heat a large nonstick skillet or griddle over medium heat. Cook farls in batches for 4–5 minutes per side until golden brown and crisp, turning once.
08 - Serve warm, generously spread with salted butter.