Carabaccio: Florentine Onion Soup

Onion soup is mostly associated with French cooking, but there are many versions throughout Italy. This one, from Florence, is unique in that it contains not just onions — the star ingredient — but also split peas. This touch makes the soup extra hearty, just the remedy for chilly February days and nights. 

Red onions are what you want for this soup; their sharpness mellows as they cook, slowly, over low heat, but they retain their rich flavor. This recipe is slightly adap