The Best French Onion Soup

5 from 10 votes
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Rich, warm, and super savory, this French onion soup contains beef stock and caramelized onions, topped with toasted bread and melted cheese – a warming favorite for chilly days!

French onion soup in a small bowl topped with cheesy toast

If you’re drawn to the idea of caramelized onions combined with a rich and intense beef stock, enhanced with a splash of wine, and topped with a cheesy bread topping, you’re not alone. Luckily, that’s precisely what this French onion soup is! Slowly caramelizing the onions adds impressive depth to the ingredients, bringing out their natural sweetness and making for a thick, rich vegetable-based soup packed with depth and the perfect “stick to your ribs” winter soup.

Three small bowls with French onion soup topped with cheesy toast

Ingredients

Ingredients for French onion soup
  • Onions: And lots of them for a truly delicious veggie French onion soup. I like to use yellow onions.
  • Garlic: Adjust the amount to personal taste.
  • All-purpose Flour: Necessary for thickening the soup. Cornflour also works.
  • Olive oil: Or another neutral cooking oil. Butter/ghee would also work for even sweeter results.
  • Thyme: I used dried thyme, as it’s all I had. However, you could use double the amount of fresh thyme (using a couple of thyme sprigs).
  • Beef stock: I use this rich flavorful beef stock. Use homemade vegetable stock if you prefer vegetarian French onion soup.
  • Dry white wine: Alternatively, Brandy, sherry, or vermouth also work.
  • Sugar: This is technically optional depending on what onions you use and how sweet you prefer the soup. I use just a pinch of sugar to enhance the natural sweetness.
  • Bread: For bread, choose baguette slices or any crusty artisan bread that won’t get soggy in the soup. Croutons are also an option.
  • Cheese: Gruyere is the traditional cheese for French onion soup. However, Swiss cheese, Gouda, Jarlsberg, or a combination of mozzarella and cheddar would work. DON’T use pre-shredded cheese as it lacks flavor and may contain additives, affecting the soup’s taste.

Video tutorial

How to make French onion soup

Prepare the caramelized onions: First, peel and thinly slice the onions. I do this by slicing off the root and stem ends of the onion. Then chop it in half (from top to bottom), then place the onion halves cut-side down and slice (make cuts about ¼-inch apart).

Then, heat the olive oil in a large deep-bottomed soup pot over medium-high heat. Once hot, add the onions and cook, stirring often, for around 10 minutes until they’re beginning to wilt.

Meanwhile, chop one of the garlic cloves and add it to the onions along with the sugar and thyme.

Stir well, lower the heat to medium, and cook for 30 minutes. Stir less often at first (every 4-5 minutes), increasing frequency towards the end (every 1-2 minutes) to prevent burning as the onions caramelize. If pieces start burning, lower the heat. Stir well to lift browned bits from the pot. Deglaze with a splash of your stock or wine before adding flour, if needed.

Steps for cooking onions

Adjust the time if needed until you achieve soft and slightly sweet onions with a rich golden brown color. Feel free to move on to the next step earlier if you like the taste when the onions are slightly less caramelized. For more tips, check How To Caramelize Onions!

Make the Broth: Add the flour to the pan and stir well to combine, allowing it to cook for 2 minutes. Then add the wine (use it to deglaze the pan and scrape up any browned bits from the bottom of the pan) and beef/veggie stock, stirring well, and bring the mixture to a rolling boil.

Skim and foam from the surface of the soup, then lower the heat to a gentle simmer, cover with a lid, and allow it to cook for a further 40-45 minutes.

Steps for simmering French onion soup

Assemble and Serve: First, preheat the oven grill. Then, toast the bread slices under it (usually 5-8 minutes total). Pour the soup into oven-safe bowls/ramekins (wide enough for your bread pieces), filling them ¾ way. Then place a piece of the toast in each bowl and top with freshly grated cheese until you can’t see the soup below (don’t be stingy!).

Broil for several minutes until the cheese has melted and is beginning to bubble. It’s best to broil them around 6 in/15cm away from the heat source. Serve piping hot!

Steps for adding cheesy bread topping to onion soup

If you don’t have oven-safe bowls, make cheesy garlic bread to serve with the French onion soup instead. Simply spread toasted bread on a baking sheet, add cheese, and broil before adding to the soup. This keeps the bread from getting too soggy

Storage

  • Make-Ahead: Prepare the French onion soup without the cheesy bread topping up to 4 days in advance. Store in the fridge. Then reheat when needed and add the topping (the flavor will develop in the fridge and taste even better!).
  • Freeze: Freeze the cooled soup (without bread/cheese topping) in airtight containers or Ziplock bags (portioned, with headspace) for up to 3 months. Thaw in the refrigerator before reheating or speed up the process in a hot water bath.
  • Reheat: Gently reheat the soup in the microwave or on the stovetop, adding extra broth or water if needed.
A spoonful of French onion soup

Recipe tips and notes

  • Don’t over-brown the onions: or you may end up with an overly bitter soup.
  • Avoid over-broiling the cheese: aim for golden and lightly bubbling to keep it gooey and melty. Over-browning it will make it crispy and miss out on the gooey texture.
  • Cut the onions uniformly: that way, they’ll caramelize evenly too. Using a mandoline (carefully) to slice the onions can help for consistent results.
  • Adjust the amount of sugar: I like to add “just” enough for a very subtle sweetness. However, feel free to adjust the amount to your taste.
  • Don’t rush the soup: possibly the most crucial tip of all. This French onion soup is all about the rich flavor of the slowly caramelized onions, so don’t try any shortcuts!

If you try this French onion soup recipe, let me know how it goes in the comments below. I’d appreciate a recipe card rating and would love to see your recipe recreations – tag me on Instagram @Alphafoodie!

The Best French Onion Soup

5 from 10 votes
By: Samira
Rich, warm, and super savory, this French onion soup contains beef stock and caramelized onions, topped with toasted bread and melted cheese – a warming favorite for chilly days!
Prep Time: 5 minutes
Cook Time: 1 hour 25 minutes
Total Time: 1 hour 30 minutes
Servings: 6

Equipment

Ingredients 
 

  • 1.1 lb onions 3 large ones. Yellow onions are best. You could also use a combination of sweet onions with yellow onions.
  • 3 Tbsp olive oil OR butter/ghee
  • 0.7 oz garlic 2 large cloves
  • 2 Tbsp all-purpose flour or cornstarch
  • 1 tsp dried thyme or double the amount of fresh thyme leaves
  • 1/2 cup white wine dry; OR sherry, brandy, or vermouth; check notes for a wine-free version
  • 6 cups beef stock or vegetable stock
  • 1/2 Tbsp sugar omit if preferred
  • French bread baguette or crusty artisan bread works best.
  • Gruyere, frehsly shredded or Swiss cheese, Gouda, Jarlsberg, or a combination of mozzarella and cheddar.

Instructions 

Caramelize the onions

  • Peel and thinly slice the onions. I do this by slicing off the root and stem ends of the onion. Chop it in half (from top to bottom), then place the onion halves cut-side down and slice (make cuts about ¼-inch apart).
  • Heat the olive oil in a large deep-bottomed soup pot/Dutch oven over medium-high heat. Once hot, add the onions and cook, stirring often, for around 10 minutes until they’re beginning to brown.
    If you notice pieces burning rather than just browning, reduce the heat slightly. Make sure to stir well to lift up browned bits from the bottom of your pot each time you stir. You can lightly deglaze the pan with a splash of your stock or wine as needed at the end of the process, too (before adding flour).
  • Meanwhile, chop one of the garlic cloves and add it to the onions along with the sugar and thyme.
  • Stir well, reduce the heat to medium, and cook for 30 minutes. Stir infrequently to begin (every 4-5 minutes) and more so towards the end (every 1-2 minutes), as they’re more likely to burn once reduced/caramelized.
    Adjust the time if needed until you achieve soft and slightly sweet onions with a rich golden brown color. Feel free to move on to the next step earlier if you like the taste when the onions are slightly less caramelized.

Make the broth

  • Add the flour to the pan and stir well to combine, allowing it to cook for 2 minutes. Add the wine (use it to deglaze the pan and scrape up any browned bits from the bottom of the pan) and beef/veggie stock, stirring well, and bring the mixture to a rolling boil.
  • Skim and foam from the surface of the soup, then lower the heat to a gentle simmer, cover with a lid, and allow it to cook for a further 40-45 minutes.

Assemble and serve

  • Preheat the oven grill. Then, toast the bread slices under it (usually 5-8 minutes total).
  • Pour the soup into oven-safe bowls/ramekins (wide enough for your bread pieces), filling them ¾ way. Then place a piece of the toast in each bowl and top with freshly grated cheese until you can’t see the soup below.
    If you don't have oven-safe bowls, make cheesy garlic bread to serve with the French onion soup instead. Simply spread toasted bread on a baking sheet, add cheese, and broil before adding to the soup.
  • Broil the ramekins for several minutes until the cheese has melted and begind to bubble. It's best to broil them around 6-inches/15cm away from the heat source. Serve piping hot!

How to store

  • To make ahead: Prepare soup without cheesy bread topping up to 4 days in advance. Store in the fridge. Then reheat when needed and add the topping (the flavor will develop in the fridge and taste even better!).
    Freeze: Freeze the cooled soup (without bread/cheese topping) in airtight containers or Ziplock bags (portioned, with headspace) for up to 3 months. Thaw in the refrigerator before reheating or speed up the process in a hot water bath.
    Reheat: Gently reheat the soup in the microwave or on the stovetop, adding extra broth or water if needed.

Video

Notes

Don’t over-brown the onions: or you may end up with an overly bitter soup.
Avoid over-broiling the cheese: aim for golden and lightly bubbling to keep it gooey and melty. Over-browning it will make it crispy and miss out on the gooey texture.
Cut the onions uniformly: that way, they’ll caramelize evenly too. Using a mandoline (carefully) to slice the onions can help for consistent results.
Adjust the amount of sugar: I like to add “just” enough for a very subtle sweetness. However, feel free to adjust the amount to your taste.
Don’t rush the soup: possibly the most crucial tip of all. This French onion soup is all about the rich flavor from the slowly caramelized onions, so don’t try any shortcuts!
Course: Appetizer, Main, Side, Soup
Cuisine: European, French
Freezer friendly: 3 Months
Shelf life: 3-4 Days

Nutrition

Calories: 142kcal, Carbohydrates: 15g, Protein: 1g, Fat: 7g, Saturated Fat: 1g, Polyunsaturated Fat: 1g, Monounsaturated Fat: 5g, Sodium: 945mg, Potassium: 153mg, Fiber: 2g, Sugar: 7g, Vitamin A: 509IU, Vitamin C: 7mg, Calcium: 31mg, Iron: 1mg

Nutrition information is automatically calculated, so should only be used as an approximation.

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