A comforting bowl of French-inspired warmth
When the days shorten and I find myself pulling the curtains at half-past four, French onion soup feels like the perfect antidote. Slow-cooked onions transformed into a deep mahogany sweetness, floating in a rich broth, capped with bubbling Gruyère that strings with every spoonful—it’s the kind of dish that makes winter not only bearable but positively appealing.
The patience required for the onions is rewarded tenfold. The scent of them gently caramelising fills the kitchen with a perfume so nostalgic that I always linger by the hob, wooden spoon in hand, convinced that this is the most comforting smell in the world. And when finally topped with a golden, cheese-draped crouton, it turns into a meal that feels almost ceremonial.
I like to think of this as a soup for evenings when you want to take your time. It’s not a rush-to-the-table recipe like my creamy roasted butternut squash soup, which can be whipped up with little fuss. Instead, it rewards unhurried cooking, a bottle of wine open on the counter, and maybe a record spinning in the background.
If rich onion soup speaks to you, you might also enjoy my chestnut and mushroom soup, which shares the same earthy intensity, or the potato leek soup with pancetta crumble, which carries a more delicate balance of creaminess and savoury crunch. Also have a look at our winter warmer soup collection for more inspiration.
Ingredients for French onion soup
- 1.2 kg onions (a mix of yellow and red works well), thinly sliced
- 60 g unsalted butter
- 2 tbsp olive oil
- 2 tsp sea salt
- 1 tsp sugar
- 3 cloves garlic, minced
- 2 tbsp plain flour
- 250 ml dry white wine
- 1.5 litres beef stock (or vegetable stock for vegetarian)
- 3 sprigs thyme
- 2 bay leaves
- 1 baguette, sliced into rounds
- 200 g Gruyère cheese, grated
- Freshly ground black pepper to taste
Ingredient notes
Onions are, naturally, the heart of this recipe. A mix of red and yellow gives both depth and brightness, but if you’ve only got one type, it will still work beautifully. It’s worth slicing them evenly so they caramelise at the same pace, avoiding burnt stragglers.
Gruyère is the classic choice, its nutty sharpness melting into luscious strands. If you can’t find it, Comté or Emmental make good stand-ins. Vegetarian versions of Gruyère-style cheeses are increasingly easy to find, making it possible to enjoy this soup without compromise.
Instructions
Set a heavy-bottomed pot over medium-low heat. Add butter and olive oil, then tumble in the sliced onions with salt and sugar. Cook gently, stirring often, for 40–50 minutes until the onions are deeply caramelised, golden brown, and sweet. Don’t rush this stage—it’s what gives the soup its depth.
Stir in the garlic and flour, cooking for two minutes to eliminate any rawness. Deglaze with white wine, scraping the bottom of the pot to release caramelised bits. Pour in the stock, tuck in thyme and bay leaves, and bring to a simmer. Cook uncovered for 30 minutes, stirring occasionally. Remove the herbs, season with pepper, and ladle into ovenproof bowls.
Place baguette slices on top of each bowl, cover with Gruyère, and place under a hot grill until the cheese is molten and bubbling. Serve straight away, though mind your tongue—the cheese top will be lava-like at first bite.
Cooking techniques explained
The most important step is patience with the onions. They need to cook low and slow to coax out natural sugars without catching. High heat might tempt you, but it risks bitter, burnt patches. A splash of water midway can help prevent sticking if the onions dry out.
The gratinéed topping is another hallmark. Using bowls that can withstand the grill makes a difference, as it allows the bread to soak into the broth while the cheese melts. Don’t skimp on the Gruyère—the joy of this dish is that molten, stringy layer.
What to serve with French onion soup
This soup is hearty enough to stand alone, but I like a crisp green salad alongside, dressed simply with mustard vinaigrette to cut through the richness. A small plate of cornichons or pickled shallots also works as a sharp counterbalance.
If serving as a dinner party starter, I’d keep portions modest and follow with something lighter, perhaps roast chicken with lemon or pan-fried sea bass. The soup sets a rich tone, so the following course should contrast rather than compete.
Wine and beer pairings
A Burgundy Chardonnay complements the soup perfectly, with its buttery texture echoing the Gruyère while acidity balances the richness. Alternatively, a light-bodied Pinot Noir brings cherry brightness that pairs beautifully with caramelised onion sweetness.
For beer, a malty brown ale works wonders, its roasted notes echoing the slow-cooked onions. A crisp pilsner, on the other hand, provides a refreshing lift that prevents the dish from feeling overly heavy.
Frequently Asked Questions
Can I use vegetable stock instead of beef?
Yes, vegetable stock keeps the soup vegetarian and still delivers depth. If you’d like another vegetarian-friendly winter warmer, try my potato leek soup.
How do I stop my onions from burning?
Cook them gently and stir often. Adding a splash of water or stock if they begin to stick helps. Patience is key—rushing leads to char rather than caramel.
Can I prepare French onion soup in advance?
Absolutely. The soup base can be made a day or two ahead, stored in the fridge, and reheated. Add the bread and cheese just before serving to keep them crisp and molten.
What bread works best for the topping?
A sturdy baguette is traditional, but sourdough works well too. Avoid very soft bread, which will collapse into mush.
Tips for success with French onion soup
Take your time with the onions—they should be dark, sweet, and jammy before adding anything else. This stage lays the foundation, and shortcuts will only leave you disappointed with bland results. Choose heatproof bowls with enough depth to hold both soup and toppings. It’s worth investing in proper soup crocks if you plan to make this regularly, as they help replicate the classic restaurant finish at home.
Recipe variations
For a stronger flavour, replace part of the stock with dry sherry or Madeira. Both bring a richer sweetness that complements caramelised onions. If you’d like a lighter dish, top with toasted bread rubbed with garlic but skip the cheese. It’s not traditional, but it makes a more everyday version that still delivers all the oniony depth.
Storage and reheating French onion soup
The soup base keeps well in the fridge for up to 3 days. Store without the bread topping. Reheat gently on the hob, then finish with the bread and Gruyère under the grill. It also freezes for up to 3 months—thaw overnight in the fridge before reheating.
Slow-Cooked French Onion Soup with Melted Gruyère Topping
Ingredients
- 1.2 kg Onions (a mix of yellow and red works well), thinly sliced
- 60 g Butter unsalted
- 2 tbsp Olive oil extra virgin
- 2 tsp Sea salt
- 1 tsp Sugar
- 3 cloves Garlic minced
- 2 tbsp Flour plain
- 250 ml White wine dry
- 1.5 l Beef stock or vegetable stock for vegetarian
- 3 sprigs Thyme
- 2 Bay Leaves
- 1 Baguette sliced into rounds
- 200 g Gruyère cheese, grated
- Black pepper to taste, freshly ground
Instructions
- Set a heavy-bottomed pot over medium-low heat. Add butter and olive oil, then tumble in the sliced onions with salt and sugar. Cook gently, stirring often, for 40–50 minutes until the onions are deeply caramelised, golden brown, and sweet. Don’t rush this stage—it’s what gives the soup its depth.
- Stir in the garlic and flour, cooking for two minutes to eliminate any rawness. Deglaze with white wine, scraping the bottom of the pot to release caramelised bits. Pour in the stock, tuck in thyme and bay leaves, and bring to a simmer. Cook uncovered for 30 minutes, stirring occasionally. Remove the herbs, season with pepper, and ladle into ovenproof bowls.
- Place baguette slices on top of each bowl, cover with Gruyère, and place under a hot grill until the cheese is molten and bubbling. Serve straight away, though mind your tongue—the cheese top will be lava-like at first bite.