March 4, 2025
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When I mention French onion soup to friends, they all make a face. I understand, it sounds strange. But please try this at least once, I promise it isn’t what you think! The onions turn sweet, the white wine comes through, and the cheese on top makes the whole thing unforgettable.
Onion soup is a big deal in our house. We make it regularly through the winter and we always have a smile on our faces eating it.
Table of Contents
Where French onion soup comes from
French onion soup is Parisian, and it earned its reputation at Les Halles, the vast central market that fed Paris until the 1970s. The market restaurants that made it famous are still named in the histories: Au Pied de Cochon, La Poule au Pot, Chez Baratte. It was breakfast for the porters hauling crates before dawn, and it was what you ate at four in the morning coming out of a nightclub, which is why it also picked up the name soupe d’ivrognes, which means drunkards’ soup.
And there’s another good reason to making french onion soup. Onions are genuinely good for you, especially in winter. They’re a natural anti-inflammatory, they have antibacterial and antiviral properties, and they’re particularly good for the respiratory tract when you have a cold or a cough. So if you skip the bread and the cheese and just drink the broth, you’ve basically made yourself a very French, very comforting and tasty remedy!
Ingredients
- Onions — ordinary yellow onions are what you want, sliced evenly so they caramelise at the same rate.
- Butter — a generous amount, and it’s what the onions cook down in for the best part of an hour. Pick good French butter if you can.
- Stock — the body of the soup. Homemade stock or store bought.
- Dry white wine — deglazes the pan and lifts everything that has caught on the bottom, which is where a lot of flavour is sitting.
- Baguette — day-old, so it holds its shape and soaks up broth without dissolving into it.
- Comté or Gruyère — the crust on top. Comté has more depth, Gruyère melts a little more readily. A mix of both is genuinely worth doing.
- Thyme and bay — quiet aromatics simmered in and lifted out before serving.
How to make French onion soup
1. Slice the onions evenly and start them low
Peel and slice all of them thinly and to a consistent thickness, because uneven slices means some catch and burn while others are still pale. Into a heavy cocotte with the melted butter and a generous pinch of salt, which draws the water out and gets them going.
2. Caramelise slowly, and don’t turn the heat up
Thirty to forty minutes minimum, over genuinely low heat, stirring often. This is the whole soup. Rushed onions go soft and slightly bitter; slow onions turn sweet, jammy and deep amber. The colour should build gradually, and when they look almost too dark, they’re ready. If you haven’t got the time, make something else today.
3. Deglaze with the wine
Turn the heat up, pour in the wine, and scrape the base of the pan hard with a wooden spoon. All those sticky brown bits are concentrated onion flavour, and leaving them stuck to the pot is throwing away the best part. Let it bubble down for a minute.
4. Add the stock and let it come together
Stock, thyme and bay, then a gentle simmer with the lid on for twenty minutes so the flavours settle into each other. Season at this point rather than earlier, since the liquid reduces and concentrates whatever you added at the start.
5. Toast the bread and cheese it
While the soup simmers, slice the day-old baguette thickly, toast the rounds until golden, then pile grated cheese on and grill until bubbling. Toasting first is what stops the bread turning to mush the moment it meets the broth.
6. Gratinée and serve immediately
Fish out the thyme and bay, ladle into ovenproof bowls, float the cheesy croutons on top and scatter over more cheese. Under a hot grill until blistered and golden. Then straight to the table, because breaking through that cheese crust with a spoon is the best part of eating it.
Tools for this recipe
Check out my favorite kitchen essentials and cookware!
- Use a heavy cast iron cocotte that spreads heat evenly across the base, since forty minutes of caramelising in a thin pan gives you hot spots that scorch the onions while the rest stay pale.
- Use ovenproof soup bowls so the whole thing can go under the grill for the final gratinée rather than being assembled at the table.
- Use a sharp knife because 750g of onions is a lot of slicing and a blunt knife makes it miserable.
Tips for success
- Slice the onions with a mandoline if you have one: even thickness is what gives even caramelisation, and it saves your eyes twenty minutes of work.
- Salt the onions at the start: it draws out their water, which speeds up the first stage and stops them catching before they’ve begun to soften.
- If the pan starts to catch, add a splash of water or wine: scrape the base and carry on. Those brown bits dissolve back into the onions and deepen the flavour rather than ruining it.
- Use day-old bread, and toast it anyway: fresh bread disintegrates into the soup within a minute. Stale and toasted holds its raft long enough to get to the table.
- Grate the cheese finely: it’s the crust, not a garnish, and thin cheese won’t form the sheet you need to break through.
- Warm the bowls before ladling: cold ceramic takes the heat out of the soup and slows the grilling.
How to store it
- In the fridge: The soup base keeps 3 days covered and improves for the first two as the onion flavour settles. Store it without the bread and cheese, and add those fresh when you serve.
- In the freezer: The soup base freezes very well for up to 3 months, which makes a double batch worth the effort of all that slicing. Freeze in portions and thaw overnight in the fridge. Never freeze it with the croutons in.
- Assembled: Doesn’t keep at all. Once the bread is in the soup it’s on a clock, so gratinée only what you’re serving.
More soup recipes to try
Variations
- With a splash of cognac or port: added with the wine, or a spoonful stirred in right at the end. Common in brasserie versions and it adds real depth.
- Mixed cheeses: gruyère for the melt, Comté for the tang, or Beaufort if you want something more complex.
- With a slice of Reblochon: laid on the crouton instead of grated cheese, which melts into something extremely rich.
FAQ
How long do you really need to caramelise the onions?
At least 30 to 40 minutes over low heat, and longer is better. This is where all the flavour comes from, and rushing over high heat gives you soft, slightly bitter onions instead of sweet, jammy ones.
Can you make French onion soup ahead of time?
Yes, and it’s better for it. The soup base keeps 3 days in the fridge or 3 months in the freezer. Add the bread and cheese fresh when you serve.
What cheese is best for French onion soup?
Comté or Gruyère, grated finely. Comté has more depth and Gruyère melts a little more easily, so a mix of both gives you the best of each.
Why is my onion soup bitter?
The onions were cooked too fast or too hot, or a little caught and burned on the base. Keep the heat low, stir often, and deglaze with a splash of water if anything starts to stick.
What bread should I use?
Day-old baguette, cut thick and toasted before it goes on the soup. Fresh bread falls apart in the broth almost immediately.
Prep Time 20 minutes 
Cook Time 50 minutes 
Total Time 1 hour 10 minutes 
Servings 4Description
Ingredients
- 750 gr onion
- 75 gr unsalted butter
- 2 l vegetable stock
- 125 ml dry white wine for example a Waitrose Blueprint White Burgundy
- 1 baguette
- 200 gr Comté cheese or Gruyère or Emmental
- 1 thyme optional, for aroma
- 1 bay leaf optional, for aroma
- salt and black pepper
Equipment
Instructions
1. Caramelise the onions
- Peel and finely slice the onions. Melt the butter in a large heavy pan over gentle heat, add the onions and a generous pinch of salt. Cook slowly, stirring often, for 30–40 minutes, until soft, golden and deeply caramelised. Don't rush this, it's the soul of the soup.
2. Build the base
- Pour in the white wine to deglaze, letting it bubble while you scrape up the sticky bits from the bottom of the pan. Add the stock, thyme and bay leaf. Bring to a gentle simmer, cover, and cook for 20 minutes. Season with salt and pepper to taste.
3. Prepare the bread
- While the soup simmers, preheat the grill (or oven to 200°C). Slice the baguette into thick rounds and toast on a baking tray until golden. Top each generously with grated cheese and return to the grill until bubbling.
4. Finish and serve
- Remove the thyme and bay. Ladle the hot soup into ovenproof bowls, float the cheesy croutons on top, scatter over more cheese, and grill for a few minutes until gratinéed. Serve immediately, piping hot.
Notes
- Take your time with the onions. The deeper the colour, the richer and sweeter the soup.
- A mix of Gruyère and Comté gives the best balance of melt and tang.
- Day-old baguette holds up in the soup without falling apart.
- The soup base keeps 3 days in the fridge. Add the croutons fresh.
Share your feedback and spread the love!
If you try this recipe, I’d love to hear how it turns out! Leave a ★★★★★ rating and your thoughts in the comments, it helps fellow French foodies discover this recipe too. Snap a photo and tag @obviously.french on Instagram. Come talk about it in our Facebook group. And don’t forget to save this recipe to Pinterest so you’ll always have it handy for your next French-inspired meal!
This recipe sounds absolutely stunning! Can’t wait to give it a go
It’s a classic and so easy to make, enjoy!