Wash the lettuce and cut into large pieces (about 3cm).
In a saucepan add olive oil and sauté the onions slightly.
Add the pork and sauté too.
Add the salt, the pepper, and the water, cover the saucepan and cook (add extra water if needed and let boil until the meat to become soft, about 40 minutes).
When the pork is almost ready add the lettuce, celery and parsley and cook for 15 minutes.