Peel and wash the potatoes and cut them into 1/2 centimetre thick slices. Heat four tablespoons of oil in a large pan. Fry the potato slices in them in portions until crispy brown.
Then place all the slices in the pan and continue to fry over a medium heat for ten minutes. Peel and finely chop the onions and garlic. Add the last five minutes to the pan. Season with salt and pepper.
Whisk eggs and cream, season with salt and pour over the potatoes. Cover and allow to set on low heat for 15 to 20 minutes. Shake the pan from time to time so that the tortilla does not touch the bottom.
Turn the tortilla over onto a plate. Heat the rest of the oil. Slide the tortilla into the pan with the browned side up and fry for another four minutes. Arrange on a plate and serve sprinkled with parsley.