First, peel the boiled potatoes.
If you have a ricer, use it to rice the potatoes, if not, just mash them.
Add the butter and salt. Taste the potatoes at this point, add more salt if needed, then very lightly mix in the sifted flour.
Turn out onto a floured workspace and gently fold over until smooth.
Divide into 4 or 5 equal portions and form each into a ball.
Roll one ball out to about ¼″ thick, then prick with a fork and cut into quarters or sixths.
Repeat with the rest of the balls of dough.
Heat a pan or griddle to (almost) high heat.
When the pan is hot, cook the scones until brown on each side.
Place on a clean dish towel, then cover with the other half to cool.
