What Cheese Typically Goes On French Onion Soup?

Cozy yet classy, and simple yet satisfying, homemade French onion soup is one of those dishes that seems to deliver more than the sum of its parts. It only involves a few ingredients: onions, beef broth, bread, and cheese. But it's that last part — the cheese — that really turns the soup from good to great, adding rich savory flavor and a gorgeously gooey consistency. The traditional cheese of choice is Gruyère, and there are several reasons why it works so well.

Hailing from the Gruyère region in Switzerland, this Alpine cow milk cheese has an unmistakable nutty, earthy, and slightly fruity flavor profile. This distinctive aroma and full flavor of Gruyère is partly due to the fact that the milk is not heated up before it is curdled during the cheesemaking process. When melted on top of French onion soup, the taste manages to perfectly complement both the sweetness of the caramelized yellow onions and the luxuriously savory broth.

The texture of the cheese is key, too. You need something that melts easily but doesn't become oily, which can rule out options like mozzarella and hard cheeses like parmesan. Gruyère is a great melting cheese, which is why it's also a key ingredient in fondue or a simple croque monsieur recipe. When broiled, the appetizing golden color, rich aroma, and melty mouthfeel of Gruyère-topped toasts is an integral part of French onion soup — and certainly not just a mere garnish.

The taste of Gruyère cheese changes as it ages, evolving from mild, sweet, and grassy to something sharper and more robust. The texture also becomes more granular and crumbly. For these reasons, it's best to stick to a younger cheese for French onion soup, as it will melt better, and its flavor won't dominate the other ingredients. Aged Gruyère — which is considered to be any wheel aged more than 10 months, often labeled as "réserve" — is better suited to arranging a great cheese board.

For a truly traditional flavor, look for Gruyère AOP, or Appellation d'Origine Protégée. This means the cheese has a protected designation of origin, and is sourced from and produced in a designated region of Switzerland under specific guidelines. Genuine Gruyère adds truly decadent deliciousness for a next-level French onion soup.

If you do want to switch things up, however, try adding another cheese such as parmesan to the Gruyère for an extra boost of rich umami flavor. Parmesan is the cheese Ina Garten sprinkles on French onion soup – and though she uses it on its own, you'll get a meltier texture by combining it with Gruyère. Or, switch the Gruyère for Comté, another Alpine cheese from France. It's made in the Franche-Comté Jura mountains, and has many similarities to Gruyère, not least in terms of flavor.