This Traditional French Onion Soup is made with caramelized onions, a bit of smoked bacon, and a good homemade beef stock. It's topped with a slice of toasted baguette and melted Gruyère. The onions take about an hour to caramelize properly, but it's worth the wait.
I learned this recipe at Le Cordon Bleu, and I still make it the same way today. It might look like something from a restaurant, but you don't need to be a chef to pull it off.
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What Is Traditional French Onion Soup
French Onion Soup is probably one of the most famous soups in the world. It is one of these fancy-looking dishes we tend to order in a restaurant because we think it is difficult to make at home.
A Traditional French Onion Soup is made with caramelized onions slowly braised in a good homemade beef stock flavored with vermouth (or sherry), bay leaves, and thyme.
The addition of a piece of smoked bacon gives a slight smokiness to the French Onion Soup so I strongly advise using it. This onion soup is best when served with a slice of crusty baguette or Bolillo - Crusty Mexican Bread Rolls that is covered with melty, delicious Gruyère cheese mixed with some good quality Parmesan.
What Onions are Best?
The two main ingredients of a good French Onion Soup are onions and homemade beef stock. I use mainly yellow onions with the addition of some red onions. Yellow onions have a rich onion taste, and they become sticky and sweet when caramelized.
Red onions have a sharp and deep flavor and less sweetness. If you find your soup too sweet, increase the number of red onions and use fewer yellow onions.
Ingredients You'll Need
Please scroll down to the recipe card below for the full ingredients list with measurements, complete recipe method, recipe notes, and nutritional information.
- Onions - I use a mixture of yellow onions and red onions. See "What Onions are Best?" above for how the ratio affects sweetness.
- Beef stock - A good quality homemade beef stock is essential for a rich and flavorsome French Onion Soup. Store-bought ones usually lack flavor and richness which will leave you with a blend and weak soup. Use homemade Chicken Stock instead if you find making your own beef stock time-consuming. Or if you really want to use store-bought beef stock, try buying the best one.
- Bacon - A whole smoked bacon is added to the soup for a slightly smoky flavor. You can omit it if you prefer so.
- Vermouth - You can substitute vermouth with sherry. Skip the alcohol if you are cooking for kids or for a non-alcoholic version.
Garnish for French Onion Soup
- Cheese - Gruyère is the main cheese to use for this Traditional French Onion Soup recipe. I add freshly grated parmesan as it adds a nutty, salty flavor that develops a tasty crust under the broiler.
- Baguettes - I use homemade sourdough baguettes but shop-bought baguettes are perfectly fine too. A crusty roll like Bolillo also works well if you don't have a baguette on hand.
- Garlic - Rubbing the baguette slices with garlic adds a hint of garlic taste without overpowering the soup.
How to Make the Perfect French Onion Soup
Caramelize the Onions
To make the soup, start by slicing your onions. Try to slice them finely for perfect and quick caramelization.
Place a Dutch oven or a heavy-based pan on low heat and add the butter.
When the butter melts, add the sliced onions to the pan.
Gently cook the onions until nice and soft, stirring occasionally to avoid them burning. That usually takes around 15 minutes.
When they are soft and translucent, turn the heat up to medium-high to start the caramelization. Keep stirring the onions to avoid burning them, and be patient at that stage.
We need a nice golden-brown color on onions without burning them. Burnt onions will give a bitter taste and an unpleasant look to the soup. If the onions aren't caramelized enough, the soup will lack the sweetness coming from the onions.
Build the Soup
When the onions are golden brown and release their sweetness, add the garlic and cook for another minute. Use vermouth or sherry to deglaze the pan then add the flour.
Give it a good stir then deglaze the pan again with some of the beef stock to dissolve all the brown bits stuck to the surface.
Add the whole bacon, bay leaves, thyme, and black pepper along with some more of the beef stock. Only add just enough stock to make a thick soup. You can always add more later if it's too thick at the end of the cooking period.
Bring it to a boil, turn the heat to low, and let it gently simmer for 45 minutes.
Garnish the Soup and Serve
Preheat the grill to 200° C (390° F) and start preparing your garnish while the soup is cooking. Thinly slice the baguette, rub them with garlic, and place them in the oven for a few minutes until lightly toasted.
When the soup is cooked, remove the whole bacon, bay leaves, and thyme stalks. Check the seasoning and add some salt if needed. Ladle the soup in individual oven-proof bowls or ramekins.
Put a slice (or two!) of baguettes on top of the soup, top them with your cheese mixture, and place the ramekins in the oven. Let them under the grill until the cheese is bubbly and slightly golden.
If you don’t have oven-proof individual bowls or ramekins, you can grill the cheesy baguettes separately on a tray and place them on soup ladled in bowls.
Recipe Tips From The Chef
- If you find your soup too sweet, increase the number of red onions and use fewer yellow onions.
- A good quality homemade beef stock is essential for a rich and flavorsome French Onion Soup.
- Try to slice the onions finely for perfectly even and quick caramelization.
- Cook the onions slowly and patiently until the natural sugars are released, and the onions are transparent and have a deep golden brown color. Do the caramelizing without burning them. Burnt onions will give a bitter taste and unpleasant look to the soup.
- Using a wide heavy-based pan will help caramelize the onions evenly and also help reduce the caramelizing time.
- Short on time? Caramelize the onions in a slow cooker instead: cook on low for 8-10 hours, stirring once or twice, then finish the soup on the stove.
- No oven-safe bowls? Toast the baguette slices with cheese under the broiler on a baking sheet instead, then float them on top of the soup right before serving.
Serving Suggestions
You can serve this delicious, rich soup as an appetizer for special occasions or gatherings, such as Thanksgiving or Christmas dinner parties. This recipe serves 6 guests as a starter/appetizer.
If you want to serve it as a main dish, you can serve it with a bowl of simple salad such as Çoban Salatası, Arugula Spinach Salad, or Gavurdagi Salatasi (Turkish Tomato Walnut Salad).
Storage and Reheating Instructions
Let the soup cool completely, then store it (without the bread and cheese) in an airtight container in the fridge for up to 5 days, or in the freezer for up to 3 months.
To reheat, bring it to a boil on the stovetop, or microwave in 2-minute bursts, stirring halfway through. Once hot, pour into oven-safe bowls, top with toasted bread and grated Gruyère and Parmesan, then broil until bubbly and browned.
Make Ahead
You can make the soup itself up to 3 days ahead and keep it in the fridge without the bread and cheese. This is handy if you're serving it for a dinner party or don't want last-minute prep. Reheat gently on the stove, then add the toppings and broil just before serving.
Recipe FAQs
The best option for Traditional French Onion Soup is Gruyère cheese mixed with a bit of Parmesan. However, you can use other hard cheeses such as Provolone, Gouda, Fontina, and Swiss cheeses.
Bitterness almost always comes from burnt onions. Caramelizing takes patience: keep the heat low to medium and stir regularly so the onions cook down slowly and evenly instead of catching and scorching. If they start sticking, add a splash of water or stock to loosen them rather than turning up the heat.
Yes. The vermouth or sherry adds a bit of depth but isn't essential. Just leave it out and use a little extra beef stock in its place.
It's best not to. Freeze the soup on its own, without the bread and cheese, then add fresh toasted bread and cheese after reheating and broil until bubbly for the best texture.
As written, no, because it uses beef stock and a little smoked bacon. To make it vegetarian, swap in a good-quality vegetable stock and omit the bacon. The caramelized onions still do most of the flavor work.
Related Recipes
For more delicious French recipes why not try:
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I hope you enjoy the process of making this simple yet incredibly flavorful Traditional French Onion Soup as much as you enjoy eating it! 🙂
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Traditional French Onion Soup
Ingredients
For the Soup
- ½ stick butter (50 grams)
- 3 ½ oz finely sliced red onion (100 grams)
- 1 lbs finely sliced yellow onion (450 grams)
- 1 clove garlic (finely chopped)
- 3 tablespoon vermouth or sherry
- 3 tablespoon plain flour
- 3 cups beef stock
- ½ oz smoked bacon (15 grams)
- 2 bay leaves
- 3 sprigs thyme
- ¼ teaspoon freshly ground black pepper
- salt to taste
For the Garnish
- 1 baguette
- 1 clove garlic (cut in half)
- 1 cup Gruyère cheese (finely grated)
- ½ cup Parmesan cheese or any hard Italian cheese (finely grated)
Instructions
Caramelize the Onions
- To make the soup, start by slicing your onions. Try to slice them finely for perfect and quick caramelization.
- Place a Dutch oven or a heavy-based pan on low heat and add the butter.
- When the butter melts, add the sliced onions to the pan.
- Gently cook the onions until nice and soft, stirring occasionally to avoid them burning. That usually takes around 15 minutes.
- When they are soft and translucent, turn the heat up to medium-high to start the caramelization.
- Keep stirring the onions to avoid burning them and be patient at that stage. We need nice golden brown color on onions without burning them. Burnt onions will give a bitter taste and unpleasant look to the soup. If the onions aren't caramelized enough, the soup will lack the sweetness coming from the onions.
Build the Soup
- When the onions are golden brown and release their sweetness, add the garlic and cook for another minute.
- Use vermouth or sherry to deglaze the pan, and then add the flour.
- Give it a good stir then deglaze the pan again with some of the beef stock to dissolve all the brown bits stuck to the surface.
- Add the whole bacon, bay leaves, thyme, and black pepper along with some more of the beef stock. Only add just enough stock to make a thick soup. You can always add more later if it's too thick at the end of the cooking period.
- Bring it to a boil, turn the heat to low, and let it gently simmer for 45 minutes.
Garnish the Soup and Serve
- Preheat the grill to 200° C (390° F) and start preparing your garnish while the soup is cooking.
- Thinly slice the baguette, rub them with garlic, and place them in the oven for a few minutes until lightly toasted.
- When the soup is cooked, remove the whole bacon, bay leaves, and thyme stalks. Check the seasoning and add some salt if needed.
- Ladle the soup in individual oven-proof bowls or ramekins.
- Put a slice (or two!) of baguettes on top of the soup, top them with your cheese mixture, and place the ramekins in the oven.
- Let them under the grill until the cheese is bubbly and slightly golden.
- If you don’t have oven-proof individual bowls or ramekins, you can grill the cheesy baguettes separately on a tray and place them on soup ladled in bowls.
Notes
- This recipe makes about 6 servings when served as a starter or appetizer.
- The vermouth or sherry is optional. Leave it out and use a little extra beef stock instead if you'd rather not cook with alcohol.
- Don't have oven-safe bowls? Broil the bread and cheese separately on a baking sheet, then float them on top of the soup just before serving.
- Burnt onions will turn the soup bitter, so keep the heat low and be patient while caramelizing. See the Top Tips section above for more on getting this right.
- Make ahead: cook the soup up to 3 days in advance and keep it in the fridge without the bread and cheese. Reheat gently on the stove, then add the toppings and broil just before serving.
- Store leftover soup (without the bread and cheese) in an airtight container in the fridge for up to 5 days, or freeze for up to 3 months.
Danilo says
The whole family enjoyed these flavors and this soup is a family favorite a great recipe and will make again!