The Best Type Of Cheese For Traditional French Onion Soup

A warm crock of French onion soup is a cozy, hearty dish that you can enjoy as an appetizer or as a meal in itself. In its simplest form, it's made with caramelized onions in a broth that's topped with baguette slices and cheese, but it's rooted in technique and contains plenty of ingredients that give the broth its signature taste. According to tradition, there's only one cheese for this soup that stands above the rest: Gruyère.

While other cheeses are sometimes substituted, Gruyère is earthy, mild, and slightly nutty, ultimately making it the perfect complement to the rich flavors in the broth. Gruyère hails from Switzerland, and it's beloved by well-known chefs and food connoisseurs alike — even Anthony Bourdain recommended it in this soup. Plus, it melts easily, so whether you're slicing it in a single layer or freshly shredding it, this cheese bubbles and browns to perfection the moment it's placed under the broiler.

This cheese is named after the small town of Gruyères, Switzerland, but it's popular in this particular dish due to the town's proximity to France. If you want the most traditional and authentic variety of this cheese, then you need to use the kind labeled Gruyère AOP. That name denotes a cheese made in the Swiss region of origin that follows all of the same preparation styles and techniques as traditional Gruyère.

To be even more specific, look for a fairly young Gruyère AOP for your soup, preferably one that has only aged about six months. That's because this cheese dries out as it ages, so to achieve the meltiest texture, look for one that's only a few months old. Avoid packaging with terms like reserve, surchoix, or vieux, all of which indicate that the cheese is at least 10 months old. If those are all you can find, though, they'll work — they'll just have deeper flavors and will be more difficult to melt (this is also why aged cheese isn't the best idea for your mac and cheese sauce).

Of course, it's not mandatory that you use Gruyère cheese in your French onion soup — that's just the way it was originally made. According to legend, the smell of Gruyère helped conceal the scent of alcohol, so hundreds of years ago, those who had a little too much to drink would make soup topped with Gruyère in order to hide their night out. This soup-and-cheese pairing was also just convenient; since the soup originated in France, Gruyère was a perfect match, as it was produced just over the border in Switzerland.

Although Le Gruyère AOP is popular in French onion soup, there are actually two different types of Gruyère: Swiss and French. The latter differs from its Swiss cousin in that it has a slightly sweeter flavor. Visually, it also has small holes in it that aren't present in the Swiss. Different varieties of French Gruyère include Comté and Beaufort. Both would technically work in French onion soup, but the Swiss variety is more common.