French onion soup is a classic for a good reason – flavorful, savory, cheesy, simply irresistible. It’s so easy to make at home and requires just a couple of ingredients to make it. You will need some patience to caramelize the onions but it will reward you with an amazing soup that your family will rave about!
French onion soup
French onion soup or “soupe à l’oignon gratinée” is a classic French soup made with caramelized onions, beef broth, and topped with cheesy bread.
What are caramelized onions? Caramelized onions are sliced onions that are cooked long enough to caramelize the sugars that naturally occur in onions. They are light brown in color, very sweet, and have a deep savory flavor. I have a separate article about caramelizing onions.
Ingredients
Here’s what you need to make this delicious soup:
- Onions – I used yellow onions – these are my favorite onions for this soup. I don’t like to use sweet onions (such as vidalia) – they come out too sweet.
- Clarified butter – is my fat of choice for cooking the onions if I have it on hand. If not, I will use half regular butter and half olive oil or just olive oil. I don’t like to use regular butter because it burns more quickly (you can use it to cook the onions but you need to be more careful and stir the onions more often to make sure they don’t burn). Clarified butter doesn’t burn easily like regular butter and it’s very easy to make at home.
- Broth – this is, after the onions, the most important ingredient for this soup. Traditionally, beef broth is used in this recipe. If you have a good quality beef broth, this is great, but making your own beef broth can be time-consuming and expensive, so most of us reach for store-bought beef broth. Please, taste your store-bought broth before you use it in this soup – most of the store-bought beef broth taste really bad. If you don’t have a good quality beef broth it’s better to use half beef broth and half chicken broth or just chicken broth. Store-bought chicken broth is usually better quality than beef broth. French onion soup is really tasty with good chicken broth. If you’re making lots of beef roasts/dishes where you have leftover beef meat or bones, you can freeze them to make homemade beef broth later. I really love onion soup with duck broth or goose broth made from roast duck or roast goose carcass and leftover bones (the instructions for the broth can be found in the post). It makes a really fantastic onion soup – we make it every time when we have duck/goose broth.
- Wine – use any dry white wine. Wine is absolutely necessary for this soup – it adds flavor and acidity which balances the sweeteness from the onions. Most of the alcohol will evaporate during cooking, but not 100%.
- Brandy – it’s optional and I wasn’t very convinced if I should add it to the soup but after just one sip I was sold – it really adds great flavor to the soup. You can also use cognac.
- Thyme – you can use fresh or dried. Fresh will always taste better.
- Fresh garlic.
For the topping:
- Baguette or French bread or really any bread (stale bread is also great!) that you have.
- Cheese – the best is Gruyere cheese which is traditional for this soup – it’s an amazing flavorful cheese that adds ton of flavor to the soup. Gruyere alternatives are Swiss cheese, Provolone, Appenzeller, Emmentaler, Comte, Fontina, Jarlsberg, or Raclette. Here you can find more recipes using Gruyere cheese.
Ingredients that other recipes use, and I do not:
- Flour – many recipes use flour to thicken the soup which is not very authentic. I tried adding just 1 tablespoon of flour to this recipe and wasn’t a fan. The soup will be thickened anyway with cheese and baguette.
- Worcestershire sauce – it’s a good idea to add 1 ts to the soup if you’re using chicken broth – it will deepen its flavor.
- Sugar – some add sugar to the onions to speed up the caramelization process. I don’t like to add it because it makes the onions too sweet.
Step by step instructions
Caramelize the onions: Peel the onions, cut them in half, and then into 1/4-inch (7mm) slices. Heat the clarified butter or butter/olive oil in a large, heavy-bottomed pot over medium heat. When hot add the onions and 1 teaspoon of salt. Cook them for about 45-50 minutes until caramelized – they will be soft and light brown in color. At the beginning you can stir the onions from time to time but as they darken you will need to stir more often. While stirring make sure to scrape all the brown bits on the bottom of the pot. Be careful not to burn the onions – they will be bitter. Anytime the onions look like they are starting to burn on the bottom of the pot – stir them with a spatula or deglaze the pot with a small amount of water.
Caramelizing onions can not be sped up (without sacrificing the flavor or the texture). They really need time to develop an amazing deep flavor.
On the other hand, you can not caramelize onions for too long – they will be bitter.
Salting the onions at the beginning of cooking helps to soften them more quickly.
Photo 2 – this is how the onions will look like after 15 minutes of cooking time.
Photo 3 – this is how they look like after 30 minutes.
Photo 4 – these onions were cooked for 45 minutes and are done!
Add finely chopped garlic and thyme to the pot. Cook for 30 seconds.
Add the wine, cook until it’s reduced in volume in 3/4.
Add the broth. Bring to a boil then simmer over low heat for 15 minutes (while the soup is cooking, you can make the cheesy bread, see below).
Add the brandy. Bring the soup to a boil then immediately take the pot off the heat. Season the soup with salt and pepper.
Cut the baguette into thick slices and place them on a baking sheet lined with parchment paper. Bake at 425°F (220°C) for 7 minutes or until golden.
The bread needs to be toasted so it can soak up the soup, if it’s too soft it will become mushy very quickly. If you have stale bread you can omit this step – you can use even a couple of days old baguette for this recipe!
Top the toasted baguette slices with shredded cheese, bake until melted, about 5 minutes.
Assemble: ladle soup into bowls. Sprinkle with a small amount of cheese then put 1-2 slices of baguette in the soup. Sprinkle with thyme leaves and enjoy!
NOTE: Traditionally, the soup is poured into oven-safe bowls, then topped with toasted bread and sprinkled with cheese. Then it is baked until the cheese is melted and bubbly. I’m not a fan of this preparation method – the soup gets extremely hot and because the bowl is also hot, it cools down very slowly making the soup difficult to eat. That’s why I prefer to make the cheesy bread separately and serve it on top of warm soup – it really tastes the same in my opinion and it’s more convenient to eat.
Top tips
There are three main reasons why French onion soup can taste bad:
- It’s too sweet – caramelized onions are not balanced by acidic ingredients. In this recipe dry white wine and brandy provide acidity. If your soup came out too sweet you can add some sherry vinegar/white wine vinegar/lemon juice to reduce the sweetness even more.
- It’s made with bad-quality broth – as mentioned before in the Ingredients section, store-bought chicken broth is usually better than beef broth. If using store-bought beef broth, make sure it tastes really good, otherwise, it’s better to use chicken broth. Homemade good-quality beef broth would be ideal but other good alternatives are chicken/duck/goose broth.
- Burned onions – result in bitter soup. Be careful to not burn the onions/cook them until they are too dark in color – you don’t really need to cook them until they are dark brown – golden brown/light brown is enough. Don’t rush the onions, they need time to caramelize, if you cook them over higher heat they will just burn/become too dark without caramelizing which is a chemical reaction that takes time.
Storage
Keep this soup in the fridge for up to 3-4 days. It reheats very well. You can also reheat your cheesy bread (stored separately) in the oven until warm and the cheese is soft. Cheese croutons taste best freshly made.
It can also be frozen for 3 months. You can also freeze caramelized onions so the next time you’re making this soup it will go much quicker!
Recipe FAQ’s
Yellow onions are traditional and a good choice for French onion soup.
Caramelizing the onions, the use of wine, beef broth, and croutons with Gruyere cheese on top.
Either the onions have been burned or a bad-quality broth has been used.
French onion soup doesn’t need to be thickened – it will be thickened naturally with cheese and bread that will soak up the soup and thicken it. If you want your soup thicker (which will impair its flavor), you can add 1-2 tablespoons of flour to the soup. Traditional French onion soup is rather thin and this is what I prefer.
Alternatives for Gruyere cheese are: Swiss cheese, Provolone, Appenzeller, Emmentaler, Comte, Fontina, Jarlsberg, or Raclette.
French onion soup is traditionally served in lion head bowls, which are deep but not very wide porcelain bowls. You can use any oven-safe bowls if you want to bake the soup along with croutons or just any bowl if you want to serve your soup with already-made cheese croutons on top (this is what this recipe is calling for).
This soup is pretty rich so light sides such as green salad or roasted chicken are good options.
More delicious French recipes
- Baked Ratatouille Recipe (confit byaldi)
- Pistou Soup – French vegetable soup
- Strawberry Rhubarb Galette
- Braided Brioche
- Cinnamon Palmiers
- French Onion meatballs
Did you make this recipe? RATE THE RECIPE or tell me in the COMMENTS how you liked it! You can also add a photo of your dish. It would make me very happy and will help other readers. Thank you!!
French Onion Soup
Ingredients
for the soup:
- 1/4 cup clarified butter (4 tablespoons), or 2 Tbsp olive oil + 2 Tbsp regular butter
- 3 lbs yellow onions 1.4kg
- 1 teaspoon salt
- 4 cloves garlic
- a couple of sprigs fresh thyme or 1/2 teaspoon dried thyme
- 3/4 cup dry white wine
- 8 cups beef broth* see notes
- 2 tablespoons brandy
- salt and pepper to taste
additionally:
- 1/2 large baguette
- 1 tablespoon olive oil
- 8 oz Gruyere cheese 230g
Instructions
- Caramelize the onions: Peel the onions, cut them in half, and then into 1/4-inch (7mm) slices. Heat the clarified butter or butter/olive oil in a large, heavy-bottomed pot over medium heat. When hot add the onions and 1 teaspoon of salt. Cook them for about 45-50 minutes until caramelized – they will be soft and light brown in color. At the beginning you can stir the onions from time to time but as they darken you will need to stir more often. While stirring make sure to scrape all the brown bits on the bottom of the pot. Be careful not to burn the onions – they will be bitter. Anytime the onions look like they are starting to burn on the bottom of the pot – stir them with a spatula or deglaze the pot with a small amount of water.
- Add finely chopped garlic and thyme to the pot. Cook for 30 seconds.
- Add the wine, cook until it’s reduced in volume in 3/4.
- Add the broth. Bring to a boil then simmer over low heat for 15 minutes.
- While the soup is cooking, make the cheese croutons: Cut the baguette into thick slices and place them on a baking sheet lined with parchment paper. Bake at 425°F (220°C) for 7 minutes or until golden. Top the toasted baguette slices with shredded cheese, bake until melted, about 5 minutes. Set aside.
- Add the brandy to the soup. Bring to a boil then immediately take the pot off the heat. Season the soup with salt and pepper.
- Assemble: ladle soup into bowls. Sprinkle with a small amount of cheese then put 1-2 slices of baguette in the soup. Sprinkle with thyme leaves and enjoy!
Notes
- Please only use beef broth in this soup if you have good-quality broth – taste it before using it in soup. Most of the store-bought beef broth doesn’t taste very good. If you don’t have a good quality beef broth you can use half beef broth and half chicken broth or just chicken broth. French onion soup made with good chicken broth is really good. Another great option is duck broth or goose broth made from bones and carcass leftover from roast duck or roast goose – they made fantastic onion soup.
- If you use chicken broth for this soup, you can deepen its flavor with Worcestershire sauce.
- Gruyere cheese substitutes: Swiss cheese, Provolone, Appenzeller, Emmentaler, Comte, Fontina, Jarlsberg, or Raclette.
- Traditionally, the soup is poured into oven-safe bowls, then topped with toasted bread and sprinkled with cheese. Then it is baked until the cheese is melted and bubbly. I’m not a fan of this preparation method – the soup gets extremely hot and because the bowl is also hot, it cools down very slowly making the soup difficult to eat. That’s why I prefer to make the cheesy bread separately and serve it on top of warm soup – it really tastes the same in my opinion and it’s more convenient to eat.
- Calories = 1 serving (1/6 of the recipe). This is only an estimate!
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