In a large mixing bowl, combine your cooled mashed potatoes, all-purpose flour, salt, and melted butter. Mix until a soft dough forms, about 2–3 minutes.

Lightly dust your work surface with flour and knead the dough for about 1–2 minutes until smooth.

Roll the dough into a circle approximately 1/4 inch thick.

Cut the dough into quarters to form the farls.

Heat a non-stick skillet over medium heat for about 2 minutes. Cook each farl for 3–4 minutes on each side until golden brown.

Transfer the farls to a warming plate and cover loosely with a kitchen towel.