I bought a bag of "baby potatoes" they are called. Put them on a baking tray with foil on it in hot oven for 10 minutes, turned them over after that, left for another 10 minutes, turned them over again. Then turned the oven off, left for another 10 minutes.
They shrivel up and brown off just like a large baked potato does, I think if I'd done them for 40 minutes total they would have been better, with crispier skin, but 30 minutes was fine to cook them.
I had mine sliced open with butter, most people cross cut them and push sides in so insides pop out :o)