French onion soup — or “soupe à l’oignon gratinée” — is one of my all-time favorite comfort foods. The smell of it simmering on the stove just transports me straight to Paris.
Actually, French onion soup was one of the first recipes I remember watching my idol, Julia Child, make in one of the original black-and-white episodes of “The French Chef” from the 1960s (thanks to YouTube!).
It was her who inspired me to give it a go and try to make it for myself at home. After researching so many different recipes, I always come back to Julia’s as my starting point — it tastes the closest to the real thing you get in Paris.
I’ve tweaked the recipe slightly, but I definitely have to give her credit for giving me all of the pointers for making the perfect French onion soup!
HOW TO PERFECTLY SAUTÉ AND BROWN ONIONS
I think there are two secrets to making amazing and authentic French onion soup.
The first is how you cook your onions; the traditional method of cooking the onions takes time but is totally worth it.
You start by cooking the onions in butter and a bit of olive oil in a covered pot for about 15 minutes until they are softened and translucent. Covering the pot allows them to sweat and cook evenly instead of browning straight away. If you were to skip this step, you would be left with onions that were dark along the edges and practically raw in the center.
After the initial “sweating” of the onions, you remove the lid and continue to cook and stir the onions until they are a deep golden brown color. It’s actually shocking how much the onions reduce down from the initial 8 cups that you start off with. This concentrates the flavor of the onions and makes them so sweet and tender — perfect for French onion soup. I actually love to use this same method for making caramelized onions to slather on top burgers and steaks!
ABOUT THE BEEF STOCK
The second secret to a delicious French Onion Soup is using a good beef stock. Of course homemade is always the best option (you can make your own using my Homemade Beef Stock recipe).
Nevertheless, it is totally possible to make a great soup using store-bought beef stock. I just recommend getting a low-sodium version so you have control over the amount of salt.
Also, adding in the wine and Cognac to the soup really adds a depth of flavor that can help enrich the taste of store-bought stock.
DO YOU NEED TO ADD WINE AND/OR COGNAC TO FRENCH ONION SOUP?
Of course not! You can absolutely leave the wine and Cognac out if you would like. That being said, they definitely give the soup an amazing depth of flavor that is so authentically French.
Now, some recipes I have tested in the past overdo it on the booze and I find that the taste overpowers the sweet, delicate flavor of the onions. This recipe has just enough so that it adds flavor, but is not overly potent. (And remember, the alcohol will boil off as the soup simmers.)
WHAT IS THE BEST CHEESE TO USE WITH FRENCH ONION SOUP?
Traditionally, Gruyère is the cheese used to top French onion soup.
This is where I stray a bit from the traditional: I have found that a blend of Gruyère and Mozzarella, with a bit of Parmesan, not only gives great flavor but also that extra-stringy quality that we all love.
I have also used Monterey Jack in the past and think it is another great option (if you have some on hand).
Start by preheating the oven to 325℉.
Peel, halve, and slice 2 ½ pounds of yellow onions. You should have roughly 8 cups in total.
In a large pot over medium heat, add 1 Tablespoon of olive oil and 3 Tablespoons of butter. Add in the sliced onions, then stir and cover.
Continue to cook over medium heat for 15 minutes, stirring occasionally, until the onions become soft and translucent.
After 15 minutes, remove the cover and stir in 1 teaspoon of kosher salt and ¼ teaspoon of sugar.
Increase the heat slightly and continue to cook the onions for another 30 minutes, stirring often and scraping any bits off the bottom of the pot as needed. Be careful not to burn the onions at this stage! If the onions begin to stick too much, you can add a bit of water into the pot and continue to stir. The onions should reduce in volume and become rich golden brown in color.
Stir in 2 Tablespoons of flour and cook for 2 to 3 more minutes, until the onions are coated in the flour and the flour is cooked through.
Add in the 8 cups of beef stock, ¾ cup dry white wine, ¼ cup of Cognac, bay leaf, pepper, and an additional 1 teaspoon of kosher salt.
Bring to a boil, reduce the heat, and simmer partially covered for 35 minutes.
Remove the bay leaf, taste the soup, and adjust any seasoning, as needed.
While the soup is simmering, cut 1 French baguette into ¾-inch rounds and place them on an oven rack or baking sheet in the oven for 15 minutes.
After 15 minutes, remove the rounds from the oven and brush each piece (front and back) with a raw piece of garlic that has been cut in half.
Place the baguette rounds back into the oven for another 15 minutes, until they are dry, crisp, and very slightly brown. Remove them from the oven and set them aside.
Combine 1 ½ cups of shredded Gruyère, 1 ½ cups of shredded Mozzarella, and ½ cup shredded Parmesan in a bowl. This is my favorite combination of cheeses, but you can use whichever cheeses you have on hand.
Turn the oven to a high broil.
In an oven-safe bowl or tureen, ladle in the French onion soup and cover the surface of the soup with the toasted baguette rounds. Generously sprinkle the top with the mixture of shredded cheeses.
Place the bowl(s) or tureen(s) on a baking sheet and place them under the high broiler for about 5 minutes, until the cheese is brown and bubbly. Carefully remove them from the oven and serve hot.
Authentic French Onion Soup
This authentic French onion soup is just like one you would find in a quaint restaurant in France. Bubbly, delicious, and topped with browned, stringy cheese… this is a French cooking staple, perfect for a cozy night in or to impress a crowd.
For the Soup
- 8 cups yellow onions, peeled, halved and ¼" sliced (about 2 ½ lbs)
- 1 Tbsp extra virgin olive oil
- 3 Tbsp unsalted butter
- 2 tsp kosher salt (I use Diamond Crystal)
- ¼ tsp white sugar
- 2 Tbsp all-purpose flour
- 8 cups beef stock (click for my Homemade Beef Stock recipe)
- ¾ cup dry white wine (or dry white vermouth)
- ¼ cup Cognac (or any other variety of brandy)
- 1 bay leaf, whole
- ½ tsp ground black pepper
For the Topping
- 1 French baguette, cut into ¾" rounds
- 2 cloves of garlic, peeled and halved (for rubbing)
- 1 ½ cups Gruyère cheese, freshly grated
- 1 ½ cups Mozzarella cheese, freshly grated
- ½ cup Parmesan cheese, freshly grated
Making the Soup
- Preheat oven to 325℉.
- Peel, halve, and slice onions to a ¼" thickness.8 cups yellow onions, peeled, halved and ¼" sliced
- In a large pot, heat olive oil and butter over medium heat.1 Tbsp extra virgin olive oil3 Tbsp unsalted butter
- Add in sliced onions. Stir and cover.
- Cook, stirring occasionally, until onions become soft and translucent (about 15 minutes).
- Remove cover. Add in sugar, along with 1 tsp of kosher salt.¼ tsp white sugar
- Increase heat slightly and continue to cook onions, uncovered, until rich golden brown in color (about 30 minutes more). Stir occasionally and scrape up any bits on bottom of pan, as needed.
- Stir in flour. Continue cooking until onions are well coated and flour is cooked (about 2 to 3 minutes).2 Tbsp all-purpose flour
- Add in beef stock, wine, Cognac, bay leaf, pepper, and an additional 1 tsp of kosher salt.8 cups beef stock¾ cup dry white wine¼ cup Cognac1 bay leaf, whole½ tsp ground black pepper
- Bring to a boil. Then, reduce heat to medium/low and simmer, partially covered, until all of the flavors have melded together (about 35 minutes).
- Remove the bay leaf. Taste for seasoning.
Toasting the Baguette Rounds
- Meanwhile, while the soup is simmering, cut baguette into ¾" rounds and place them on an oven rack or baking sheet. Toast rounds in the oven for 15 minutes.1 French baguette, cut into ¾" rounds
- Remove rounds from the oven. Brush each side of rounds with a raw piece of garlic, which has been peeled and halved.2 cloves of garlic, peeled and halved
- Continue toasting rounds in the oven until they are dry, crisp, and very slightly browned (about 15 minutes more).
- Remove rounds from the oven and set aside.
Assembling the Soup
- Turn the oven to a high broil.
- In a large bowl, mix together Gruyère cheese, Mozzarella cheese, and Parmesan cheese (or whichever combination of cheeses you wish).1 ½ cups Gruyère cheese, freshly grated1 ½ cups Mozzarella cheese, freshly grated½ cup Parmesan cheese, freshly grated
- In an oven-safe bowl or tureen, ladle in desired amount of soup. Place one or several toasted baguette rounds on top of soup, and cover generously with a handful of the cheese mixture. Repeat for each serving.
- Place bowl(s) or tureen(s) on a baking sheet and broil in the oven until the cheese is brown and bubbly (about 5 minutes).
- Carefully remove from oven. Serve hot.
- When browning the onions, you should stir frequently and scrape any bits that stick to the bottom. This ensures that they brown evenly and do not burn. If the onions begin to burn or stick too much you can add in a splash of water and continue to stir.
- You can remove the wine and Cognac from this recipe; however, they definitely give the soup an amazing depth of flavor and a more authentic taste.
- Feel free to use whichever combination of cheeses you like. Gruyère is the traditional cheese used in French onion soup. I have found the above combination of Gruyère, Mozzarella, and Parmesan gives the perfect balance of flavor and stringiness.