1. Heat the olive oil in a large pot over medium heat. Add the onion and pancetta and cook for a couple of minutes.
2. Add the carrots, fennel or celery, onion, herbs and chile flakes and cook, stirring now and then, for about 12 minutes. Turn down the heat if the vegetables start to brown too quickly. When they are cooked add the salt, garlic, and chickpeas.
3. Add the chickpea cooking liquid or water and the additional water or stock. Bring the soup to a boil, then reduce the heat to a simmer, adding more liquid if necessary, and cook for 10 minutes.
4. Add the greens to the soup and cook for another 10 minutes. Taste for salt and garnish with a drizzle of olive oil and a splash of balsamic vinegar, if desired (my addition). Add freshly ground black pepper, too, if you like.