Carabaccia is an ancient Tuscan onion soup, going back to the Renaissance. They say it was a favorite of Leonardo da Vinci—and that, as for so many other classic dishes, the recipe was brought by Catarina de’ Medici to France, where it evolved into the soupe à l’oignon we all know and love today.
You may be surprised at the taste of this soup. Like me, you may even find it a bit odd, at first. We moderns are not very accustomed to the sweet-and-sour-and spicy flavor profile, which is rarely found in Italian cookery today but was very typical of its time, as was the use of ground almonds as a thickener.
- 1 kilo (2 lbs) red onions, peeled and very thinly sliced
- Olive oil
- 100g (4 oz) of ground almonds
- 2 Tbs of wine vinegar
- Ground cinnamon
- 2 Tbs of sugar or honey
- Freshly ground black pepper
- 1 liter (1 quart) broth, typically vegetarian and preferably homemade
- Freshly grated Tuscan pecorino or Parmesan cheese
- A slice of toasted bread per person
Mix the ground almonds with the vinegar and a dash of cinnamon and set aside to macerate.
In a large pot, preferably of terracotta or enameled cast iron, braise the onions in a generous glug of olive oil with a pinch of salt, as gently as you can possibly manage, until they are well reduced, translucent and falling apart soft. Take care that they don’t darken too much or burn as they braise; if need be, add a bit of water along the way to make sure. Usually, though, the onions throw off a great deal of their our liquid and you may actually need to let this evaporate at the end. This initial braising is the key to the success of the dish—it coaxes out natural sweet flavor of the onions and provides the foundation of the soup. Taste the onions—they should be meltingly soft and intensely sweet. The whole process will take something like 45-60 minutes. Don’t rush.
When the onions are done, add the macerated almonds and mix them into the onions. Let the onions and almonds sauté for a few minutes, then add the sugar or honey, and a good grind of black pepper, and sauté for a few minutes more.
When all the flavors have melded, add the broth and simmer the whole thing gently for about 3o minutes or so. Taste and adjust for seasoning.
To serve, lay a slice of toasted bread in the bottom of each bowl, then ladle over the onion soup. Top with grated cheese and, if you like, a sprinkling of cinnamon, sugar and/or a drizzle of olive oil. Serve immediately while the soup is still piping hot.
The red onions are typically Tuscan; if you have access to the famous red onions of Certaldo, near Florence, then you will experience carabaccia at its most authentic. Modern versions of this dish tend to omit the ‘old fashioned’ elements—the almonds, vinegar, sugar and cinnamon—in favor of a purely savory approach, much more in line with contemporary Italian tastes. Meat broth can be used instead of vegetable, if you like; some recipes forego broth altogether, relying only on the natural liquid of the onions, with perhaps a bit of water to moisten things if necessary, for a very thick soup that is almost like a vegetable stew. In some recipes, individual soup bowls, topped with cheese, are run under the broiler or in a hot oven until bubbly, in the French manner.
Other modern recipes often call for a bit of carrot and celery are added to sauté along with the onions, and some call for the addition of other vegetables in season, like peas or fava beans in the spring. And some people like to crack an egg into their carabaccia at the last minute, just long enough to let the whites set, leaving the yolk still runny.