There is a reason French Onion Soup is a favorite. Loads of sweet, caramelized onions, in a beefy broth topped by thick, toasted baguette slices with melted cheese. The flavors and textures are amazing! With this recipe you can make this soup as good at home as your favorite restaurant.
This soup is the definition of rich, flavor-packed comfort food.
The flavor of the sweet onions in the rich broth will leave you craving more.
It’s a perfect soup on a chilly day. The homey textures with the toasted baguette soaking in the soup are the best!
Secrets for Making the Best French Onion Soup
Take your time. Like a great risotto, making this soup, caramelizing the onions in particular, takes some time and attention.
It’s not difficult but requires stirring the onions so they caramelize properly and do not burn.
Also like a great risotto, you’ll be paid for your effort in full and more with the amazing flavors of this soup.
Use a great quality broth. The second key is using a really tasty broth. We stick with traditional beef broth (but offer some alternatives too).
Whether you make the broth yourself or buy a boxed quality brand, give it a taste to ensure it’s delicious before starting.
There’s no question why it’s an international favorite. You’ll be thrilled with how fantastic your homemade version tastes!
Recipe Ingredients + Notes
Olive oil and Unsalted Butter. This delicious duo is heated and used when cooking the onion slices.
Yellow Onions. These are the star ingredient. When sliced the volume seems abundant but through cooking they will reduce significantly is size. Red onions can also be substituted.
Salt. We recommend Kosher salt which is a less salty tasting salt.
Black Pepper. Added with the salt and sugar when caramelizing the onions.
Sugar. Just a little bit of granulated sugar is used but it makes all the difference in the final flavor. The caramelized onions have just a touch of sweetness that is perfection.
White Wine. This is a signature flavor in classic French Onion Soup. However the wine is added, and cooked with the onions over high heat. It cooks off almost completely just leaving a bit of flavor.
NOTE: when cooked in this way almost all of the alcohol is evaporated off in the cooking process.
Beef Stock. The broth is the next most important ingredient to the onions. A quality broth with great flavor will make this a restaurant caliber soup. If in doubt taste the broth and make sure you like it.
Beef broth is traditionally used in French Onion Soup. I use low sodium preferring to control the salt level myself. If desired you can substitute chicken broth or a blend.
Thyme. Dried thyme is used when making the soup and fresh thyme sprigs can be used as garnish when serving.
Rosemary. Dried rosemary is used when making the soup and fresh thyme sprigs can be used as garnish when serving.
Baguette. This classic French bread is sliced thickly, toasted and added to the top of the finished soup. It slowly sinks into the soup creating wonderful texture in every bite.
Regular or gluten-free baguette can be used.
Gruyere Cheese. This is the traditional cheese used for this type of soup. It is a swiss cheese but without the strong distinct flavor of the holey cheese you might think of. It’s the main cheese in quiche recipes too!
It melts wonderfully in the last step under the broiler and adds delicious flavor.
Gruyere cheese can be pricey but it’s worth it. If you can’t find it or prefer a substitute use shredded mozzarella cheese.
How to Make it Gluten-Free
The only ingredient that needs to be substituted is the baguette. Use your favorite gluten-free baguette for the toasted slices.
I used Udi’s Gluten Free French Baguette which is a perfect size and texture. Any gluten-free baguette you love will work.
Broth Quality is Key
As mentioned above this is crucial to the flavor of the soup. If you make your own broth, use it! This soup is a labor of love and a special treat worthy of homemade beef broth.
Tasting the broth is a great way to decide if you like it.
I prefer low sodium stock but all stock is different so again taste it if you are unsure.
What is the best White Wine to use?
Use a dry white wine. Pinot Grigio, Pinot Gris, Sauvignon Blanc, Chardonnay that isn’t very oaky in flavor.
Some recipes use vermouth or dry sherry too. Julia Child would ALSO add some cognac before serving.
How to Make it – Step-by-Step
STEP 1. Soften the Onions.
Add the butter and olive oil in to a large Dutch oven or stock pot. Heat over medium high heat to melt the butter.
Add the onions (photo 1) and cook until softened and transparent (photo 2).
STEP 2. Caramelize the Onions.
In a small bowl mix together the salt, pepper and sugar. Sprinkle over the onions.
Continue to cook the onions (still over medium-high heat), stirring constantly, for 30 more minutes. Or until the onions are caramelized and deep golden brown in color (photo 3).
NOTE: the onions will deepen in color significantly in the last 5 minutes of cooking. Stirring constantly is key to avoid burning.
STEP 3. Cooking down the White Wine.
Increase the heat to high, slowly pour the white wine into the onions. Cook 5 additional minutes or until the wine has reduced almost completely.
NOTE: cooking out the wine in this way will remove most of the alcohol just leaving the flavor.
STEP 4. Adding the Broth.
Add the broth, dried rosemary and dried thyme. Reduce heat to simmer the soup for 20 minutes (photo 4 before cooking – photo below after cooking).
STEP 5. Finishing the Soup and Serving.
Ladle the soup into oven proof bowl. Place the bowls on a rimmed baking sheet for easier handling.
Place toasted slice(s) of baguette on top of each serving and sprinkle gruyere cheese over the bread.
Preheat the oven with broiler on. Place under the broiler until the cheese melts. Monitor closely to avoid burning.
NOTE: placing the soup on an oven rack one down from the top position will help slow the broiling process.
Recipe FAQ’s + Pro Tips
What does Caramelizing Onions mean?
Cooking onions in the butter and olive oil for a long period of time over higher heat allows their natural sugars to come out.
They become dark in color, soft, slightly sweet with incredible flavor.
Can I make it without Wine?
You can but it’s no longer French Onion Soup. The distinct flavor from cooking down the white wine is what defines the dish.
The wine also helps deglaze the pan, allowing browned bits of food stick to the pan to be scraped off during that cooking phase.
When cooking with wine as in this recipe, when all the liquid cooks off, the alcohol is almost all removed too.
You could skip the white wine step and go directly to the broth step if desired. It won’t taste exactly the same but will still be good!
Also check out our other soup recipes!
Use a Mandoline Slicer for the Onions
The onions can be sliced by hand but if you want even slices and to do it fast a mandoline slicer is the way to go. The thickness is set on the slicer and a whole onion is done in seconds.
I recommend using one with a guard to place over the onions so your fingers are nowhere near the blade.
The best way to store leftovers is to store the soup before the baguette and cheese are added.
Store the soup in a sealed jar or container for up to 4 days in the refrigerator.
When ready to serve (reheating and serving instructions):
- Heat a bowl of the soup in the microwave until hot.
- Toast baguette slice(s) under the broiler while the soup is heating.
- Add the bowl to a rimmed baking sheet.
- Add the toasted bread with shredded cheese and broil until the cheese melts.
How to Freeze It
Allow the soup to fully cool. Add it to a freezer safe container.
If using a freezer jar (versus a freezer bag) leave 1/2 inch space between the surface of the soup and the top of the jar. This is for expansion when frozen.
Freeze for up to 3 months.
Thaw in the refrigerator and follow instructions above for reheating and serving.
More Recipes You’ll Love!
- Caramelized Roasted Pumpkin
- Homemade Chicken Soup
- Caramelized Pear Upside Down Cake
- Slow Cooker Lemon and Ginger Sipping Broth
- Strawberry Key Lime Mojitos