From my Aberdonian mother-in-law
4 cups of flour
1 cup of sugar
1 pound of butter
1 pinch of salt
mix just enough to blend the ingredients, too much mixing makes it tough. push out onto a cookie sheet. Prick the surface with a fork all over. There is a technical term for this but I can't recall it now.
Bake at 350 for about 25-30 minutes, until the edges start turning golden brown.
I have made this many times and it always gets rave reviews. Try to get Irish butter. It has consistency closer to what you would get in Scotland. I also find if you can get it mixed with the butter cold but not hard, it bakes better and is flakier.
good eating