Origin of the Name
French onion soup, despite its name, didn't originate in France. Its roots are found in Roman times. The modern version, however, was refined in France, which is why it's commonly associated with French cuisine.
Caramelization Is Key
The soup's rich flavor comes from caramelizing onions for at least 40 minutes. This process, known as the Maillard reaction, converts the onions' natural sugars into a deep, flavorful base for the broth.
Bread and Cheese History
The addition of bread and cheese dates back to the 18th century. It was a way for French peasants to add calories and texture to this humble soup, transforming it into a filling meal.
Traditionally, beef broth is used, but variations exist. In the coastal regions of France, a fish stock might be the base, while in the United States, chicken broth is a common substitute.
Wine and Spirits
A splash of wine, sherry, or cognac isn't just for flavor. Alcohol can help dissolve flavors that are water-insoluble, adding complexity to the soup's taste profile. Each region has its preferred spirit.
In France, it's a starter, but elsewhere, it's often a main course. The choice of cheese varies too, with Gruyère being traditional, but others like Emmental or Mozzarella are also popular in different recipes.
Historically, onion soup was prescribed as a remedy for colds and hangovers. Onions contain phytochemicals that are thought to improve immune function, which may explain these traditional medicinal uses.