Peel the potatoes and slice fairly thinly.
Heat a generous amount of olive oil in a medium frying pan - probably about one and a half inches deep. When hot, add the sliced potatoes. Leave to cook in the pan for around 15-20 minutes until soft and golden.
Halfway through the cooking process once the potatoes have begun to soften, start to break them up a little in the pan with a spatula and continue five minutes until fully cooked and broken into process every pieces.
Beat the eggs in a bowl. Remove the potatoes from the heat and with a spatula take sections of the potatoes and press them against the side of the pan to squeeze out some of the excess olive oil before adding to the egg mixture. Repeat this process until all the potatoes have been added to the egg this mixture and then stir the mixture well until all the potatoes are incorporated into the eggs.
Heat a little oil in a clean medium frying pan and when hot, add the egg mixture to the pan. After a couple of minutes, once the mixture has set, place a plate over the pan and flip the tortilla onto the plate before sliding back into the pan to cook on the opposite side.
Leave to cook for a couple of minutes more before repeating this process one more time. Allow to cook for a couple more minutes until cooked through then serve either alone or with a crisp green salad.