Roman-Style Dried Fava Bean Soup with Pancetta and Marjoram

When I lived in Morocco, I was taught this delicious, earthy fava bean soup by the late Mario Ruspoli, an old friend who frequently came down to Tangier from Paris to visit his mother. Mario was a renaissance man: a filmmaker, an expert on beetles and whaling, and a great gastronome. His mother, Princess Marta Ruspoli, was an eccentric who believed so fervently in the myth of Atlantis that she was totally snookered by her grandchildren when