Wrap the potatoes in tinfoil and cook for 1 hour at 200 degrees, remove, unpack and let cool slightly.
Halve the potatoes, remove the potato mixture except for a small edge and chop as little as possible.
Cut the spring onions and black pudding into small cubes and mix with the potato mixture.
Whisk three eggs, season with plenty of pepper and salt and pour over the potato mixture. Fill the potato halves with it, cover each with a tiny piece of butter and bake under the grill until the surface is crispy.
This goes well with salads and a light mustard and yoghurt sauce.