Warm, cozy, and flavorful, this French onion soup is prepared with beef stock and caramelized onions. Top with croutons covered in melty Gruyere and Parmesan cheese.
How to Make the Best French Onion Soup
There are two essential components of a good French onion soup.
The first is the stock. Your soup will only be as good as the stock you are using. This soup traditionally is made with beef stock, though sometimes a good beef stock can be hard to come by and expensive to make.
If you use boxed stock, taste it first! If you don’t like the taste, don’t use it. (If you cook a lot of beef or beef roasts, save the scraps and freeze them to make a stock with later.)
French Onion Soup
Much of the success of this soup depends on the stock that you are using, and stock varies tremendously in its taste. Depending on your stock, you may need to bump up the flavor with some beef bouillon (we recommend Better Than Bouillon brand).
Taste the soup before putting it in the oven, and if it needs more seasoning, don’t be afraid to add more!
- 6 large red or yellow onions (about 3 pounds), peeled and thinly sliced root to stem (see How to Slice an Onion), about 10 cups of sliced onions total
- 4 tablespoons extra virgin olive oil
- 2 tablespoons butter
- 1 teaspoon sugar
- Kosher salt
- 2 cloves garlic, minced
- 8 cups beef stock, chicken stock, or a combination of the two (traditionally the soup is made with beef stock)
- 1/2 cup dry vermouth or dry white wine
- 2 bay leaves
- 1 tablespoon fresh thyme leaves (can also use a few sprigs of fresh thyme) OR 1/2 teaspoon dried thyme (more to taste)
- 1/2 teaspoon freshly ground black pepper
- 2 tablespoons brandy (optional)
- 8 slices (1 inch thick) French bread or baguette
- 1 1/2 cups grated Gruyere
- Sprinkling of Parmesan
- Caramelize the onions:In a 5 to 6 quart thick-bottomed pot, heat 3 tablespoons of olive oil on medium heat. Add the onions and toss to coat with the olive oil.Cook the onions, stirring often, until they have softened, about 15 to 20 minutes.Increase the heat to medium high. Add the remaining tablespoon of olive oil and the butter and cook, stirring often, until the onions start to brown, about 15 more minutes.Sprinkle with sugar (to help with the caramelization) and 1 teaspoon of salt. Continue to cook until the onions are well browned, about 10 to 15 more minutes.Add the minced garlic and cook for a minute more.
- Deglaze the pot with vermouth or wine:Add the wine or vermouth to the pot and scrape up the browned bits on the bottom and sides of the pot, deglazing the pot as you go.
- Add the stock, bay leaves, and thyme:Add the stock, bay leaves, and thyme. Bring to a simmer, cover the pot and lower the heat to maintain a low simmer. Cook for about 30 minutes.Season to taste with more salt and add freshly ground black pepper. Discard the bay leaves. Add brandy if using.
- Toast the French bread slices:While the soup is simmering, line a sheet pan with parchment paper or foil and preheat the oven to 450°F with a rack in the upper third of the oven.Brush both sides of the French bread or baguette slices lightly with olive oil (you’ll end up using about a tablespoon and a half of olive oil for this).Put in the oven and toast until lightly browned, about 5 to 7 minutes. Remove from oven.Turn the toasts over and sprinkle with the grated Gruyere cheese and Parmesan. Return to oven when it’s close to serving time and bake until the cheese is bubbly and lightly browned.
- Serve:To serve, ladle soup into a bowl and transfer one cheesy toast onto the top of each bowl of soup.Alternatively, you can use individual oven-proof bowls or one large casserole dish. Ladle the soup into the bowls or casserole dish. Cover with the toast and sprinkle with cheese. Put into the broiler for 10 minutes at 350° F, or until the cheese bubbles and is slightly browned.