In a large mixing bowl, combine the cooled mashed potatoes, all-purpose flour, salt, and melted butter. Mix until a soft, cohesive dough forms.

Turn the dough onto a lightly floured surface and gently knead for 1-2 minutes until smooth but not tough.

Roll the dough into a flat circle, about 1/4 inch thick, maintaining an even thickness.

Slice the dough circle into four wedges using a sharp knife or pizza cutter.

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

After flipping, cook for an additional 3-4 minutes to achieve a golden color and slight crispness.

Serve warm, optionally topped with butter, fried eggs, or smoked salmon.