French Onion Soup is such a classic and SO easy to make! Onions are slowly caramelized until soft and sweet, simmered with beef broth, thyme, and just a touch of sugar. It’s topped with a crispy crouton, loads of shredded gruyere cheese and broiled into a crispy, cheesy oblivion. So good!
Soups are our jam, be sure to check out this Award Winning Cheeseburger Soup, this Broccoli Cheese Soup, or this Minestrone Soup.
French Onion Soup
I still remember the first time I had French Onion Soup. It was at a fancy steak restaurant when I was about seven years old, and when I saw the next table’s bubbling hot, cheesy soup being delivered to their table, it was love at first sight.
This cheesy, brothy, onion-forward soup may seem hard to make, but it’s one of the easiest soups to make on the planet, and it only has about seven ingredients. Win! The only thing you need is a little bit of patience both to let the onions caramelize and to keep yourself from inhaling the broth before the cheese goes on to be melted into a gooey oblivion.
Here’s what’s happening:
- sweet caramelized onions bathed in butter
- salty beef broth studded with fresh thyme
- crispy croutons to soak up all that awesome French onion soup broth
- nutty gruyere cheese broiled until irresistibly crispy
Ingredients in French Onion Soup
- Butter. The French know how to cook, and no French dish is complete without a little bit of butter, including French Onion Soup. You really don’t need much, about 1 ½ tablespoons to get the onions caramelizing. I like to use unsalted butter so I can control the amount of salt that goes into the dish.
- Onions. Lots and lots of onions. When you let onions cook look and slow, they downsize tremendously. I used about 6 ½ cups of sliced onions, which equals about 3 large onions. Slice them thin.
- Sugar and salt. Sugar and salt are added to the onions in the beginning to facilitate the caramelization. Plus, the sugar compliments the sugars in the onions.
- Flour. I like to add just a few tablespoons of flour to my French onion soup to thicken it up just a touch.
- Beef broth. Use a good-quality beef broth or stock. I also like to use low-sodium, so I can control the amount of salt that goes into the dish, .
- Thyme. Fresh thyme if you’ve got it. About five sprigs.
- Croutons. I use a French baguette cut into about 1-inch slices.
- Gruyere cheese. This is arguably the best part of French onion soup. Gruyere cheese is nutty, salty, and melts PERFECTLY. I would not substitute anything for this. It can be a little bit pricey, but the other ingredients are dirt cheap so it makes up for it.
How to make French Onion Soup
- Caramelize the onions. I know it looks like a LOT of onions, but trust me, they will cook down. Start by adding the butter to a large heavy-bottomed pot. Turn the heat on medium and add the butter. Once the butter melts, add the onions, salt, and sugar. Stir to coat. Cook the onions for about 5 minutes until they start to soften.
- Once they soften a bit, turn the heat down to medium-low and cook another 10 minutes. Once they start to get super soft, turn the heat down again to low. Continue to cook the onions, while stirring every few minutes until the onions are golden brown and caramelized. It should take another 15 minutes or so.
- Add the rest of the ingredients. Stir the flour into the onions. Cook for 1 minute. Slowly stir in the broth and add the thyme. Bring the mixture up to a boil and let it simmer. Simmer until slightly thicker, about 4-5 minutes.
- Toast the croutons. While the onions cook. Add bread pieces to a sheet pan. Bake in the oven until toasted, about 5 minutes.
- Broil the cheese. Once the soup and croutons are ready to go, put one crouton on top of the soup. Cover with cheese. Place the soups on a large sheet pan and broil until the cheese has melted and started to turn brown and crispy, about 2-3 minutes.
Can I make French Onion Soup in advance?
Yes! In fact, please do! Make the soup, sans the bread and cheese from start to finish. Cool completely and store in an airtight container in the fridge or the the pot with a lid. Shred the cheese and store separately. When you’re ready to reheat, place the pot back on the stove and bring to a boil. Prepare the soup as directed.
Do I have to use Gruyere cheese?
So I would say yes. However, if you can’t find gruyere cheese, you can probably get away with using emmental or a good swiss cheese. And make sure it’s not pre-shredded. The way you get that gooey interior and crispy exterior is with freshly shredded cheese.
Substitutions and Tips and Tricks for Recipe Succeess
- Make sure to watch the onions, you don’t want them to burn. If they start to burn, turn the heat down a bit and continue to stir.
- Make sure to season as you go. Season the onion. After you add the broth, season again. After the broth has simmered with thyme, taste for seasoning again. Everyone’s palate is different and what I think is too salty or not salty enough may be different for your.
- Do not every leave your broiling cheese unattended! Cheese burns FAST. You really need to keep an eye on the soup when it’s under the broiler or you can quickly have a bad situation on your hands.
What to serve with French Onion Soup
French Onion Soup
- 1 1/2 tbsp unsalted butter
- 6 cups sliced onions
- 2 large garlic cloves, minced
- 3/4 tsp kosher salt, divided
- 1 tsp sugar
- 2 tbsp all-purpose flour
- 32 oz beef broth
- 5 sprigs thyme
- 4 slices baguette cut into 1-inch pieces
- 8 oz shredded grueyre cheese
- Preheat oven to 350 degrees.
- Heat a large heavy-bottomed pot to a medium heat. Add the butter. Once the butter melts, add the onions, garlic cloves, salt, and sugar. Stir to coat. Cook the onions for about 5 minutes until they start to soften. Once they soften a bit, turn the heat down to medium-low and cook another 10 minutes. When they start to get super soft, turn the heat down again to low. Continue to cook the onions, while stirring every few minutes until the onions are golden brown and caramelized. It should take another 15 minutes or so.
- Stir the flour into the onions. Cook for 1 minute. Slowly stir in the broth and add the thyme. Bring the mixture up to a boil and let it simmer. Simmer until slightly thicker, about 4-5 minutes.
- While the onions cook. Add bread pieces to a sheet pan. Bake in the oven until toasted, about 5 minutes.
- Pour the soup into four oven-proof French Onion Soup bowls, Once the soup and croutons are ready to go, put one crouton on top of the soup. Cover with cheese. Place the soups on a large sheet pan and broil until the cheese has melted and started to turn brown and crispy, about 2-3 minutes. Serve immediately.
All nutritional information is based on third party calculations and is only an estimate. Each recipe and nutritional value will vary depending on the brands you use, measuring methods and portion sizes per household.
Hi, cant wait to try this! Do you think almond flour would work as substitute for the all purpose flour in the recipe?? thanks so much 🙂
I have not tried it any other way. Let me know how it turns out!
Hi there! Beautiful recipe and pictures. I love French onion soup. Do you mind sharing where you got your grey bowls in your pictures? Thanks!
I got them awhile ago. It may have been Sur La Table, Target or Pottery Barn.
My favorite soup of all time
This was a big hit for dinner tonight. I’m not fond of cooking, but I love French onion soup. Well worth the effort!! First time I’ve had Gruyere cheese and it was delicious. I’ll definitely be making it again soon.
Sounds too yummmy. Going to try soon. Thank you.
I made this last night for dinner and it was so good. With this time of the year being so busy, nice to know this didn’t take long to make and was so warm, filling and part of a nice dinner. Thank you for sharing your recipe!
I didn’t see the garlic mentioned in the directions. Did I miss it? Can I assume that it is cooked with the onions?
Yes, I apologize. I just changed the recipe card and updated with the garlic. Thank you for bringing it to my attention.