Scotch pies were traditionally made with a mutton filling, but that's quite hard to find these days, so lamb is used. Scotch pies are similar to pork pies, in that the meat is fairly dry, not in a sauce, and it is raw when it goes into the pie. What makes scotch pies special is that the pastry is very thin and dry, the lid is recessed below the rim of the pie, and the filling is greasy to soften the pastry.