French Onion Soup is cozy, rich, and full of sweet caramelized onions in a savory broth. The onions cook low and slow until they are deep golden brown, then they simmer with chicken and beef broth. Top each bowl with crunchy croutons and plenty of melted cheese for a delicious finish!
Want all the classic French onion soup flavors but don’t have as much time? My Easy French Onion Soup is a quicker option when you are craving that same cozy bowl. And for more comforting soups to make this season, check out my Fall Soup Recipes!
Ingredients & Substitutions
- Salted butter: Butter adds richness as the onions cook. Unsalted butter can be used; just adjust the added salt to taste.
- Kosher salt: Salt helps season the onions as they cook and brings out their flavor. Add more at the end if needed.
- Yellow and sweet onions: The combination gives the soup a nice balance of savory and sweet onion flavor. You can use all yellow onions or your preferred combination of onions. Slice them evenly so they cook at the same rate.
- Chicken broth: Chicken stock can be used in the same amount. Homemade chicken broth also works well.
- Beef broth: Use your favorite beef broth or beef stock. For a richer soup, you can use a low-sodium broth and adjust the salt yourself.
- Worcestershire sauce: Adds savory, umami flavor to the broth. Soy sauce can be used in a pinch, but it will change the flavor slightly.
- Fresh parsley and thyme: Fresh herbs add flavor to the broth. You can use ½ teaspoon dried parsley and ¼ teaspoon dried thyme if needed.
- Balsamic vinegar: A small amount adds acidity and balances the sweetness of the caramelized onions. Red wine vinegar can be used instead, although the flavor will be slightly different.
- Black pepper: Freshly ground black pepper adds a little seasoning. Add it to taste.
- Homemade Croutons: If you really want this recipe to stand out, make my homemade croutons! (Seriously, they are so good, but don’t eat them all before adding them to the soup!) They work especially well because they hold up under the hot broth and melted cheese. Store-bought large croutons can also be used.
- Gruyère cheese: Gruyère is classic for French onion soup because it melts beautifully. Swiss cheese can be used instead.
- Asiago cheese: Asiago adds a sharp, savory flavor to the topping. Parmesan can be substituted, although it will have a slightly different flavor and does not melt quite the same way.
Tips for the Best French Onion Soup
- Slice the onions evenly. This helps them cook at the same rate and gives you a more consistent texture throughout the soup.
- Don’t rush the onions. The onions need time to soften and become deeply golden. Keep the heat at medium-low and stir occasionally to prevent them from sticking or burning.
- Scrape the bottom of the pot. As the onions cook, browned bits will build up on the bottom. Use a splash of broth to loosen them and stir them into the soup for extra flavor.
- Taste before adding more salt. The broth, Worcestershire sauce, butter, and cheese can all add salt, so wait until the soup is finished before adjusting the seasoning.
- Use oven-safe bowls. The bowls go directly under the broiler, so make sure they are labeled oven-safe and can handle high heat.
- Don’t walk away from the broiler. The cheese can go from perfectly golden to burned quickly. Keep a close eye on the bowls while they broil.
- Use sturdy croutons. Large, firm croutons hold up well under the broth and cheese without becoming completely soggy right away.
FAQs
Can I use a different type of onion?
Yes! Yellow onions are the best choice for their balance of sweetness and savory flavor, but you can use all yellow onions or swap in sweet or red onions. Just be sure to slice the onions evenly, so they cook at the same rate.
Why do the onions need to cook for so long?
The long cooking time gives the onions time to soften and develop their deep golden color and rich flavor. Keep the heat at medium-low and stir and scrape the bottom of the pot as needed so the onions caramelize without burning.
Can I use store-bought croutons?
Absolutely! Large store-bought croutons work well and make this soup even easier. Choose sturdy croutons that can hold up under the broth and melted cheese.
Can I use a different cheese?
Yes. Gruyère is a classic choice for French onion soup, but Swiss cheese is a good substitute. You can also use Parmesan in place of the Asiago, although it will have a slightly different flavor and melt.
Can I use only beef broth?
You can, but I like using both chicken and beef broth for a balanced flavor. Using all beef broth will give the soup a deeper, more traditional beef flavor.
Can I make French Onion Soup without broiling it?
Yes. You can ladle the soup into bowls and top each with cheese, then serve with the croutons on the side. However, broiling the cheese on top gives you that bubbly, golden finish that makes this soup so good.
Why is my French Onion Soup too salty?
The salt can add up from the salted butter, broth, Worcestershire sauce, and cheese. For better control, use low-sodium broth if possible and wait until the soup is finished cooking before adding more salt.
What To Serve With French Onion Soup
French Onion Soup can be a meal on its own, especially with the cheesy croutons on top. If you want to serve it with something else, here are a few easy options:
- Green salad: A simple side salad adds something fresh and light alongside the rich soup.
- Crusty French Baguette: Serve extra bread for dipping into the savory broth.
- Garlic bread: A warm, buttery side pairs well with the onions and broth.
- Roasted vegetables: Roasted carrots (I also have air fryer carrots) or roasted Brussels sprouts make an easy side.
- Simple sandwich: A crispy grilled cheese or turkey sandwich can turn the soup into a heartier meal.
How To Store French Onion Soup
French Onion Soup is best stored without the croutons and cheese on top. Store the soup separately, then add fresh croutons and cheese when reheating and serving.
Refrigerator: Let the soup cool completely, then store it in an airtight container in the refrigerator for up to 4 days.
Reheating: Reheat the soup gently on the stovetop over medium-low heat or in the microwave until heated through. Add fresh croutons and cheese, then broil until the cheese is melted and bubbly.
Freezer: Freeze the soup without the croutons or cheese in freezer-safe containers for up to 3 months. Leave a little space at the top for expansion.
To serve after freezing: Thaw the soup in the refrigerator overnight, then reheat gently. Add fresh croutons and cheese before broiling.
French Onion Soup
Ingredients
Soup
- ½ cup (½ stick / 57 g) salted butter
- 1 teaspoon kosher salt, plus more to taste
- 3 large yellow onions + 1 large sweet onion, thinly sliced (about 10 cups total)
- 4 cups (32 ounces) chicken broth
- 4 cups (32 ounces) beef broth
- 1 tablespoon Worcestershire sauce
- 2 sprigs fresh parsley
- 1 sprig fresh thyme
- 1 tablespoon balsamic vinegar
- Freshly ground black pepper, to taste
Topping
- 4 cups homemade croutons
- 2 cups (216 g) Gruyère cheese, shredded
- 2 cups (160 g) Asiago cheese, shredded
Instructions
- Melt the butter in a large Dutch oven or heavy-bottomed pot over medium heat. Add the sliced onions and kosher salt. Stir to coat the onions in the butter.
- Cover and cook for 15 to 20 minutes, stirring once or twice, until the onions have softened and released a lot of liquid.
- Uncover and reduce the heat to medium-low. Continue cooking, stirring every few minutes and scraping the bottom of the pot, until the onions are very soft and deeply golden brown, about 35 to 50 minutes more. If the bottom of the pot starts to get too dark, add a splash of broth and scrape up the browned bits. The total onion cooking time should be about 50 to 70 minutes.
- Once the onions are deeply golden, add a splash of the chicken broth and scrape the bottom of the pot to loosen any remaining browned bits.
- Add the remaining chicken broth, beef broth, and Worcestershire sauce. Tie the parsley and thyme together with kitchen twine and add to the pot. Bring the soup to a simmer, then reduce the heat and cook gently for 20 to 25 minutes.
- Remove and discard the herb bundle. Stir in the balsamic vinegar. Taste and season with additional salt and black pepper as needed. Keep the soup warm over low heat.
- Preheat the broiler. Arrange 4 oven-safe bowls or crocks on a rimmed baking sheet. Ladle the hot soup into the bowls, filling each about two-thirds full.
- Top each bowl with about 1 cup of croutons. Sprinkle each with ½ cup Gruyère and ½ cup Asiago.
- Broil for 3 to 5 minutes, watching closely, until the cheese is melted, bubbly, and golden in spots. Serve immediately.
Did you make this recipe?
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