Isn’t it irresistible to call them Hasselhoff? Easier to make than it sounds, the only caveat is they take longer to cook than you’d have thought. Probably better to use smallish or medium sized potatoes – mine were quite large and started to scorch before they softened.
They sell special spoons in Sweden to rest your potato on and insert the knife just to the rim of the spoon, not cutting through the potato. But an ordinary large spoon will serve just as well, all you have to be is careful not to slice through.
You can stick any herbs you like into the slots, making sure plenty of butter goes in as well.