Pod the fava beans (remove the skin if they are very big). Put the pancetta, the onion and the celery in a saucepan to sauté with the oil, stirring frequently. When the fat of the pancetta has melted, add the fava beans, moisten with hot broth and carry on cooking. When the fava beans are completely done (about 20 min.), add salt and pepper and sprinkle with chopped parsley.