Tip the cold mash into a bowl, add the melted butter, flour, baking powder and salt, and mix to a soft dough. It should be soft enough to shape but not sticky, so add another spoonful of flour if your mash was wet.
Turn out onto a floured surface and roll to about 1.5cm thick. Cut into rounds with a 8-9cm cutter, then cut each round in half so you have triangles, which is the traditional shape. Re-roll the trimmings until you have used all the dough.
Heat a flat pan or heavy frying pan over a medium heat with a wipe of oil, then fry the scones in batches for 3-4 minutes per side until they have brown patches on both sides and are hot right through.
Keep the cooked ones warm in a low oven under a clean tea towel while you fry the rest, they stay lovely and soft this way.
Serve hot with butter, or as part of a full Scottish breakfast alongside eggs, sausages and black pudding.
Any that you do not eat will keep in the fridge for 2 days and toast beautifully.