Place the potatoes and a knob of butter in a large bowl and mash together until smooth, then stir in the remaining ingredients until combined. Bring the mixture together to form a ball.
Tip out on to a surface dusted lightly with flour, roll into a round about 5 mm (¼ inch) thick and cut into six triangles.
Brush a griddle or nonstick frying pan with a little oil and add a knob of butter, then cook the scones for a few minutes on each side until golden. Serve with butter and cheese.