Ask a Florentine and they will tell you that onion soup is Tuscan, not French. The Tuscan version, known as carabaccia (pronounced kar-a-ba-cha), is documented in Renaissance recipe books—usually a soup of sliced onions stewed in vegetable broth, thickened with ground almonds, spiced with cinnamon—and it is assumed that the Florentine noblewoman Catherine de' Medici brought the recipe to Paris with her Florentine entourage when she married King Henry II (like many things the Florentines claim theirs, from crêpes to sorbet). It's even said that this soup was a favorite of the Tuscan artist and inventor (and non-meat eater), Leonardo da Vinci.
Carabaccia doesn't look like the French onion soup that you're used to. The bread—usually toasted and, if you like, rubbed with garlic—goes in the bottom of the bowl, like in most Tuscan soups, not the top. The cheese is Parmesan, not Gruyere, and the stock is a lighter vegetable stock.
Today's carabaccia is usually a mellower, earthier version of the antique ones, often with Parmesan and a runny-yolked poached egg in it to add creaminess and sustenance. I like to keep mine something that da Vinci may have eaten, so I make a vegetable stock as the base. But if you want a richer soup, feel free to make this with chicken or beef stock. (You could also take a page from the Tuscan cookbook Il Panunto Toscano from 1705, which suggests that some sausages go well in this, as does a good broth of castrated lamb.) A springtime version sees fresh peas and fava (broad) beans in here too, which freshen the soup and add color.
As Florentine journalist Aldo Santini describes, carabaccia has the “seven virtues” that were noted even in the 16th century: It satisfies hunger and thirst, it facilitates sleep and digestion, it's delicious, gives energy, and makes rosy cheeks. What more can you ask of from your dinner?
- 2 pounds (roughly 1 kg) red onions, sliced thinly
- 2 tablespoons extra virgin olive oil, plus more for drizzling
- 4 fresh sage leaves
- salt and pepper
- 4 cups (1 liter) vegetable stock
- 4 eggs
- 3/4 cup grated Parmesan cheese, plus more for serving if desired
- 4 slices crusty bread, toasted
Editor's Note: This post originally called this soup vegetarian, but since most Parmesan contains animal rennet, we've amended the terminology.