If you buy fresh octopus, tenderize it before cooking by freezing it (it also softens hitting it) or buy it frozen.
Remove octopus from the freezer the day before to thaw. (Watch it! It drains plenty of liquid)
Wash with water before cooking to remove impurities.
Place a big pot over heat with water. When it starts boiling add the octopus: take it by the head and plunge it into the water for three times in order to keep octopus stiff avoiding the skin to be detached while cooking.
Boil the octopus for about 35-40 minutes over medium heat, depending on size. Stab it from time to time in order to see when it gets softer.
In the meantime, peel, wash and chop potatoes in halves. Reserve.
When octopus is cooked, leave to stand a few minutes and place it on a platter. In the same water, cook potatoes for 15 minutes.
Cut the octopus with kitchen scissors, legs into 1 cm thick slices and head into small pieces.
We serve it on wooden plate over a bed of potatoes. Salt with coarse salt, sprinkle with paprika and add a dash of oil.