French Onion Soup
Each bowl of this soup features onions that are sugary and jam-like, broth that is cozy, bread that’s soaked in the middle and crisp around the edges, and cheese that melts into a bubbly, buttery canopy.
This recipe was written for the Arizona Republic.
Once you have perfectly caramelized onions, you need little else
Achieving perfectly caramelized onions, which is the key to flawless onion soup, requires time; and lots of it. Caramelization is a chemical process that occurs when the sugars in the onions reach a certain temperature and turn from white to golden to caramel in color. The more caramelized the onions, the deeper the color and flavor.
Pro tip: Because we want the onions to caramelize slowly over time, choose a pan that delivers consistent heat, preferably a heavy Dutch oven or stock pot.
Plan on at least 45 minutes for caramelization; the process could take up to one hour. Which onion variety should you use? Yellow onions are traditional, but you can use white or red onions, or a combination of onion varieties.
Wine is traditionally added to French onion soup, and it serves a definitive role. Wine is used during the “deglazing” step, when we scrape up the delectable, browned onion bits from the bottom of the pan and incorporate them into the soup. Much of the alcohol cooks off during this step, and the wine’s sweet, floral essence is left behind. My recipe calls white wine or vermouth, just note that you don’t need an expensive bottle. Anything that you would sip from a glass will suffice. If you want to omit the alcohol, substitute an equal amount of beef broth.
Be picky about your beef broth. Since French onion soup is simply a marriage of onions, butter, beef broth, bread, and cheese, choose good-quality broth. You want a broth that boasts a robust beef taste, not one that relies on salt for flavoring.
Pro tip: If you feel the need to bump up the flavor of your broth, add a little beef bouillon. I prefer Better than Bouillon, which is paste-like and sold in jars.
The better broths are richer and thicker and, thanks to the amount of collagen and proteins, are gelatinous when chilled. Skip the watery, salty broths, and pay an extra buck or two for really good broth. If desired, you can also use good-quality beef stock, or beef bone broth.
Use French bread and decide whether or not to toast the slices. Traditionally, the bread in French onion soup is not toasted. That means the center of each slice is soaked with flavor (and sometimes melts into the broth), while the crust is crisp and chewy. That’s the quintessential French onion soup experience, so I did not toast the bread for my soup. However, if you prefer crispier, almost crouton-like bread that will last longer in the oniony broth, toast your slices before adding them to the soup.
Gruyere is the classic cheese of choice for French onion soup. It’s nutty, sharp, and perfectly melty. But it’s often pricier than other cheeses, so please don’t pass up this soup if your grocery tab is an issue. There are great alternatives to Gruyere, including Swiss, gouda, fontina, and mozzarella.
What should you do with leftover soup?
French onion soup can easily, and successfully, be stored for later. There are no starches to soak up the broth, so it’s just as lovely days (or even months) after it’s been made. Store your leftover French onion soup, without the bread and cheese, in an airtight container in the refrigerator for up to 4 days, or in the freezer for up to 3 months. Reheat the soup in a saucepan on the stovetop and add the bread and cheese just before serving (as directed below).
French Onion Soup
Ingredients
- 3 tablespoons unsalted butter
- 5 to 6 yellow onions, 3 pounds, peeled and thinly sliced
- Salt and freshly ground black pepper
- 6 cups beef broth, beef stock, or bone broth
- 1 cup dry white wine or vermouth
- 1/2 teaspoon dried thyme
- 1 tablespoon all-purpose flour
- 1/4 loaf French bread/baguette, cut crosswise into 1/2-inch-thick slices
- 1 1/2 cups grated Gruyere cheese, or cheese of choice (see note above)
Instructions
- Melt the butter in a heavy Dutch oven or stock pot over medium heat. When the butter is melted, add the sliced onions and 1/2 teaspoon of salt, and stir to coat. Cover the pan and let the onions soften for 5 minutes.
- Remove lid and let onions caramelize until golden brown, stirring occasionally. Keep an eye on the pan and adjust the heat if onions are browning too quickly. The caramelization process will (and should) take 45 to 60 minutes. My onions took 1 hour.
- Meanwhile, warm the broth in a medium saucepan over low heat.
- Once the onions are caramelized, add the wine, and bring to a simmer, scraping up the browned bits from the bottom of the pan. Add the flour and thyme and stir to coat. Cook for 1 minute, until the thyme is fragrant.
- Gradually add the warmed broth, 1/4 teaspoon of salt, and 1/4 teaspoon of black pepper and bring to a simmer. Simmer, uncovered, for 10 minutes, until the soup thickens slightly.
- Preheat the broiler.
- Ladle the soup into individual, heat-proof, soup bowls or casseroles and place the bowls on a baking sheet. Place a slice of bread into each bowl and top each slice with the cheese.
- Place the baking sheet under the broiler and broil until the cheese melts, about 1 to 2 minutes (watch carefully, this can happen fast). Remove the soup from the oven when the cheese bubbly. Serve immediately.