In a large mixing bowl, combine your cooled mashed potatoes with all-purpose flour, salt, and melted butter. Use your hands or a fork to mix until a soft dough forms, about 2–3 minutes.

Transfer the dough onto a lightly floured work surface and gently knead for about 1–2 minutes until it becomes smooth.

Using a rolling pin, roll the dough into a circle approximately 1/4 inch thick.

With a sharp knife, cut the rolled dough into quarters, forming triangle-shaped farls.

Heat a non-stick skillet or griddle over medium heat. Place the farls onto the skillet and cook for 3–4 minutes per side until golden-brown.

Once cooked, remove the farls from the skillet and serve warm.