This traditional recipe for Bistro French Onion Soup with Croutons gives you a homemade version of a soup that is a magical combination of onions, beef stock, bread, and cheese. Meditate over the pot of slowly caramelizing onions and you can count the preparation of this soup as a bit of food therapy as well. The aroma of the soup is intoxicating, the flavor is rich and delicious, and the melted cheese and crispy croutons are the perfect topping.
It’s not easy to replicate many of the iconic French bistro menu items at home, but this Bistro French Onion Soup with Croutons is an exception. As long as you have the patience to wait for perfectly caramelized onions (no 15 minute onions here!) there’s nothing too complicated about this soup.
You will often see French onion soup served with a giant slice of bread and melty cheese on top. I find it so hard to get that perfect bite with bread, melty cheese, and soup on the spoon when you are wrangling that one big broiled crouton. I've changed the recipe to be made with smaller croutons instead of one large piece of bread so that everyone can have all of the flavors and textures on one spoonful.
I include ingredient notes here when I think they’ll be helpful, including ways to source, any preparation tips, or why I've chosen a particular ingredient. Be sure to check out the recipe card below for the full list of ingredients and their quantities!
- Onions: Use yellow or white onions and slice them into strips or rings about ½-inch thick.
- Olive Oil and Butter: A combination of oil and butter will give you the rich buttery flavor plus a little insurance that your butter won’t burn over the long cooking time.
- Dry White Wine: Use a white wine you’d drink by the glass. I opt for a Sauvignon Blanc, Pinot Grigio, or Chardonnay.
- Beef Broth: A low-sodium stock or broth will help you dial in the exact level of saltiness you prefer in the final soup.
- Thyme: Add a couple of whole sprigs of thyme to the simmering broth to add a classic herbal note to the soup.
- Gruyere or Swiss Cheese: A nutty Gruyere melts beautifully over the top of the soup and imparts gorgeous flavor. Swiss cheese is another great option for topping the soup.
- Baguette: A crusty baguette is just the thing to toast up for the croutons that top the soup. Softer breads will soak up the soup broth more quickly and fall apart in the soup as it sits.
Caramelizing the Onions
Caramelizing onions takes patience and time, but you are rewarded with deep flavor and a rich tawny color. Don’t be fooled by any recipe that tells you that onions can be caramelized in 15 minutes! Check out the stages of caramelized onions below.
Add the sliced onions, salt, butter, and olive oil to the bottom of a heavy stock pot or Dutch oven. Heat over medium heat and begin stirring to melt the butter and separate the onions.
Continue to cook the onions with occasional stirring, they will start to release their moisture and soften after 10 minutes of cooking.
After 20 minutes of cooking, the onions have softened and will start to take on some color.
At the 30 minute mark, the onions are getting more golden brown and you may need to add a tablespoonful of water to get the brown bits off of the bottom of the pot so that they don’t burn. Once the onions reach this stage, don’t walk away from them! They can easily burn without constant stirring.
Once 40 minutes have elapsed, the onions are a deep golden brown. They have reduced in volume quite a bit and are soft and jammy in texture.
Hint: If you are taking the time to caramelize a batch of onions, double it! You can use caramelized onions on sandwiches, a Caramelized Onion Dip, in pasta, or on pizza like this Caramelized Onion and Prosciutto Pizza. Simply remove the extra half of the onions at this point and refrigerate or freeze them.
Finish the Soup
Add white wine to deglaze the pot, scraping the bottom of the pot to dissolve any brown bits in the wine.
Add in the thyme sprigs, black pepper, and beef broth and continue to stir to make sure nothing is sticking to the bottom.
Bring the soup to a boil and then reduce it to a simmer. Cover the pot and allow it to simmer for 10-15 minutes. Remove the thyme stems.
Place your broiler-proof bowls on a sheet pan for easy transfer in and out of the oven. Ladle the soup equally between the four bowls.
Add the Croutons and Cheese
When the soup is almost finished simmering, heat the broiler.
Dice the baguette into 1-inch cubes. Toast the croutons briefly under the broiler until they are starting to take on color.
Divide the croutons among the soup bowls and then cover the croutons entirely with the cheese. Any bread that is exposed may burn before the cheese is melted, so tuck those croutons in under a blanket of shredded cheese!
Carefully transfer the sheet pan to the oven and broil the soup for 2-3 minutes, until the cheese is melted and bubbly and takes on a golden color.
Remove the sheet pan and soup from the oven and carefully place a bowl of soup onto a separate plate so that no one burns their hands on the bowl. Serve immediately.
Substitutions and Variations
The substitutions listed below have been tested in this recipe and work well. If you successfully make any other ingredient substitutions, let us know in the comments!
- Boost the Umami Flavor - Add a tablespoon of soy sauce, Worcestershire sauce, or balsamic vinegar to the onions after deglazing with the wine to add more rich flavor to the soup.
- Skip the Wine - Deglazing with wine adds a note of complexity to the soup, but if you’d prefer to skip the wine altogether you can deglaze with a bit of the beef stock. Consider adding one of the umami boosters above to enrich the flavor of the soup without wine.
- Swap the Herbs - Thyme is a classic herb for French Onion Soup, but rosemary, marjoram, or oregano can be used in place of thyme leaves. Remember to remove the stems before serving.
- Change Up the Alliums - Instead of using onions, make this soup with leeks or shallots instead.
Use a heavy-bottomed pot when caramelizing the onions to keep the heat consistent and avoid scorched spots that will taste bitter. I use an enameled cast iron Dutch oven.
Check that the ramekins or soup crocks that you use under the broiler are broiler safe. You do not want a cracked bowl of soup to leak all over your oven. Using the wrong soup bowl can be a hazard if it shatters in the oven or once it comes out and hits the cooler air.
This soup can be served with a simple green salad for a complete meal. You can also serve it as a starter course with another bistro favorite like steak frites. For a simple dinner party meal, see the pairing suggestions below.
Make This Recipe Kid Friendly
This soup is a tough ask at my dinner table, but I have found that kids love the idea of soup croutons in general. Try adding the croutons and shredded cheddar cheese to a bowl of tomato soup or even this Broccoli, Cheddar, Potato Soup for a special topping.
Only add the croutons and cheese right before broiling and you can happily enjoy any leftovers from this recipe. Store the soup separately from the toasted croutons and shredded cheese so that the bread doesn’t get soggy. Everything should be stored in airtight containers in the refrigerator for no more than three days.
The soup can be frozen for up to 3 months. The onions may break down a bit more once thawed, but the flavor is still rich and hearty.
Make Ahead Options
Bistro French Onion Soup reheats so well, making it a great option for a make-ahead meal. Once the broth and thyme have simmered with the onions, store the soup in the refrigerator until you are ready to serve it. You can also toast the baguette croutons ahead of time and store them in an airtight bag at room temperature.
When you are ready to serve, reheat the soup in the microwave or on the stovetop and ladle it into broiler-proof bowls. Top it with the croutons and cheese and broil.
Yes, swap the beef stock for vegetable stock when preparing the soup. Adjust the salt as vegetable stock can sometimes have more sweetness than beef stock. Also consider adding a tablespoon of soy sauce in place of the additional salt to boost the umami flavor of the soup. This won't be traditional French onion soup anymore, but it will be tasty!
I typically use yellow or white onions for the soup. Vidalia or Maui onions can work well too.
If you cook the onions too long and they turn from caramelized to just plain burnt, the soup will be bitter. There is really no going back once the onions have burned, so keep the heat to medium and add a bit of water if the pot starts to get too dark before the onions are well cooked.
More Cozy Recipes
This Bistro French Onion Soup is just the thing for a chilly weekend meal. Here are some other recipes to make for hygge vibes:
Pair this rich soup with the following recipes for a special meal:
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Bistro French Onion Soup
- 6 medium yellow onions (about 1 ½-2 pounds, sliced in ½-inch strips)
- 2 tablespoon olive oil
- 2 tablespoon butter
- 1 teaspoon kosher salt
- ½ cup white wine (a dry white is preferred)
- 6 cups low-sodium beef broth
- 2 sprigs sprigs thyme
- 6 ounces Gruyere cheese (shredded, or Swiss)
- 6 oz. baguette (diced into 1-inch cubes)
- ½ teaspoon black pepper (or to taste)
- Add sliced onions, butter, olive oil, and salt to a medium heavy-bottomed pot or Dutch oven.
- Over medium heat, cook the onions for 30-40 minutes, or until deeply caramelized. You'll have to stir them often, especially after the first 20 minutes. You may need to add a tablespoon or two of water to keep them from sticking or burning. Turn heat to medium-low if they start to cook too quickly.
- Once the onions are caramelized, deglaze the pot with the wine. Scrape with your wooden spoon to get all of the brown bits dissolved.
- Add in beef broth, pepper, and thyme sprigs. Bring the soup to a boil, then reduce the heat to maintain a simmer. Cover the pot and simmer for 15-30 minutes.
- When the soup is almost ready, heat the broiler and dice your baguette. Broil the cubes slices on a sheet pan until golden on all sides.
- Ladle soup into broiler-proof bowls or ramekins placed on the sheet pan. Divide the toasted croutons evenly over the bowls. Divide the cheese over the top of the bread, covering the bread well with the cheese.
- Broil until the cheese is bubbling and golden. Serve immediately, being careful with the hot bowls!
Nutrition facts are sometimes provided below and are calculated using an online calculator. With specific brands of ingredients and additions, omissions, or substitutions the nutrition facts may change. We encourage you to use your own nutrition facts caculator to obtain the most accurate nutrition facts for your meal.