French Onion Soup Recipe

French onion soup is all about building flavor slowly. In this version, yellow onions with a little red onion are cooked down until soft and caramelized, then simmered with white wine, beef broth, thyme, and a touch of balsamic. Toasted bread and plenty of melted cheese finish the soup under the broiler for that classic golden topping.

Growing up, I never really thought of French onion soup as being about the onions. When my mom made it, she always started with homemade beef broth made with a big beef bone, and there would often be pieces of beef left in the soup. To us, it was more of a beef soup with caramelized onions.

That changed when I had French onion soup at a tasting dinner. The flavor of the onions really stood out, and it made me rethink the way I made the soup at home.

It took me a few tries to realize that the difference wasn’t a special ingredient—it was patience. The onions need time to release their moisture, cook down, and slowly caramelize. Low and slow really is the trick.

So,What Is French Onion Soup?

French onion soup is a classic French dish made with slowly caramelized onions simmered in a rich beef broth, often enhanced with white wine and herbs. It’s topped with toasted bread and melted cheese—typically Gruyère—then broiled until bubbly and golden. The result? A deeply savory, slightly sweet, and irresistibly cheesy soup that’s been a staple in French bistros for centuries.

Though it sounds simple, the magic lies in the slow caramelization of the onions, which builds the signature depth of flavor. What started as a humble peasant dish in France has now become a beloved comfort food around the world—especially during colder months when something warm and hearty hits just right.

Why you’ll love this soup?

• Deep onion flavor – Yellow onions with a little red onion create a flavorful base with slightly different sweetness and texture.
• Balanced broth – Beef broth, white wine, herbs, and a touch of balsamic give the soup depth without overpowering the onions.
• Properly caramelized onions – Salt helps release their moisture first; a small amount of brown sugar is added only after they’ve cooked down.
• Classic cheesy topping – Toasted French bread, Gruyère, Parmesan, and mozzarella create that bubbling golden finish.

Ingredients and substitutes

• Onions – I use about 900 g (2 lb) onions, mostly yellow with a small amount of red Spanish onion. Yellow onions become mellow and sweet as they caramelize, while the red onion adds a slightly different flavor and texture. You can use all yellow onions if that’s what you have.
• Butter and olive oil – Butter adds flavor while olive oil helps cook the onions without the butter browning too quickly.
• Salt – Add it early. It helps draw moisture from the onions so they soften and reduce before caramelizing.
• Brown sugar – Just 2 teaspoons, added after the onions have reduced considerably. It helps with the final caramelization without making the soup noticeably sweet.
• Balsamic vinegar – 2 teaspoons adds acidity and depth to balance the sweetness of the onions.
• Flour – A small amount gives the broth a little body. It shouldn’t make French onion soup thick like gravy.
• White wine – Use a dry white wine you enjoy drinking. It adds acidity and helps lift the flavorful browned bits from the bottom of the pot. For an alcohol-free version, use additional broth.
• Garlic – Added after the onions have caramelized so it doesn’t burn during their long cooking time.
• Beef broth – This makes up most of the liquid, so use a good-quality broth you like the taste of. This is one point RecipeTin emphasizes heavily as well because the broth is so exposed in this particular soup.
• Thyme and bay leaves – Add savory herbal flavor without competing with the onions.
• French bread or baguette – Toast it first so it holds up better once it sits over the soup.
• Cheese – Gruyère gives the classic nutty flavor. I combine it with Parmesan and mozzarella for extra flavor, browning, and that stretchy melted-cheese finish.

How to Make French Onion Soup (Step-by-Step)

1. Cook down the onions

Heat the butter and olive oil in a large Dutch oven or heavy-bottomed pot over medium heat. Add the sliced yellow and red onions and sprinkle with salt.
Reduce the heat to medium-low and cook, stirring occasionally, until the onions are very soft and have reduced considerably in volume.

Don’t rush this stage. The onions need to release much of their moisture before they can properly caramelize.

2. Caramelize the onions

Add the brown sugar and continue cooking, stirring more frequently as the onions darken. Cook until the onions are soft, golden, and caramelized.

Watch the onions rather than the clock. If they’re browning too quickly before they’re soft, lower the heat.

3. Build the soup base

Sprinkle the flour over the caramelized onions and cook for about 1–2 minutes.
Pour in the white wine and stir well, scraping the bottom of the pot to loosen all those flavorful browned bits.
Add the garlic and balsamic vinegar and cook briefly until fragrant.
Then add the thyme, bay leaves, and beef broth.

4. Simmer

Bring to a gentle simmer, then reduce the heat, cover, and cook for about 20–25 minutes.
Remove the bay leaves and thyme stems. Taste and adjust the salt and black pepper.

5. Toast, assemble and broil

Toast the French bread on both sides. Add mozzarella and broil briefly until melted.
Ladle the hot soup into oven-safe crocks. Add a little cheese, top with the cheesy toast, then finish with Gruyère, Parmesan, and mozzarella.
Broil until bubbling and golden brown.
Watch it closely — we’re talking minutes, not “I’ll quickly answer an email” time. 😂

Tips for Perfect Caramelized Onions

Cook the onions low and slow. Salt them at the beginning to help draw out moisture, and don’t add the brown sugar until the onions have softened and reduced significantly. Stir more often as they begin to brown, and lower the heat if they start to catch on the bottom.

Pro tip: Watch the onions, not the clock. They should be soft, reduced, and golden brown before you build the soup.

Best Bread and Cheese for French Onion Soup

A French baguette or other sturdy crusty bread works best because it holds up well over the soup. Toast the slices before assembling so they don’t immediately become soggy.

Gruyère is the classic choice for its nutty flavor and good melting quality. Swiss cheese can be substituted. I use Gruyère with Parmesan and mozzarella for flavor, browning, and a good cheese pull.

Serving Suggestions

French onion soup is rich enough to serve as a light meal with a simple green salad. For a larger meal, serve smaller portions as a starter before roast chicken, beef, or another simple main course.

Storage and Make-Ahead Tips

Make the soup base up to 3 days ahead and refrigerate it without the bread and cheese. Reheat on the stovetop, then assemble and broil just before serving.

You can also freeze the soup base for up to 3 months. Thaw overnight in the refrigerator and reheat gently. Always prepare the bread and cheese topping fresh.

Tips for Success

• Give the onions time. Let them release their moisture and reduce before adding the brown sugar. Caramelization is where most of the soup’s flavor develops.
• Use a wide, heavy-bottomed pot. More surface area helps moisture evaporate, while a heavy base reduces the chance of scorching.
• Keep the heat under control. If the onions start catching or browning too quickly, lower the heat rather than trying to finish them faster.
• Use broth you actually like. There are relatively few ingredients in French onion soup, so the flavor of the beef broth comes through clearly.
• Broil at the very end. The soup should already be hot when it goes under the broiler. You’re only melting and browning the cheese, so stay close and watch it.

Easy soup recipes

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Frequently asked questions

More soups you may like

• Ground Beef Soup Recipe
• Easy Bean Soup
• Creamy Roasted Acorn Squash Soup
• Roasted Red Pepper and Tomato Soup
• Roasted Carrot and Ginger Soup (Coconut)

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