French Onion Soup
Few soups reward patience like this one. Onions cooked slowly in butter for the best part of an hour turn sweet, jammy and deep brown, then simmer in beef stock with thyme and a splash of white wine. Each bowl gets toasted baguette and a thick layer of Gruyère, broiled until it bubbles over the sides.
By Mei Lin Tan
Published
- Prep Time
- 20 mins
- Cook Time
- 1 hr 35 mins
- Total Time
- 1 hr 55 mins
- Servings
- 6 servings
How do you make French Onion Soup?
For French onion soup, cook 1.5 kg sliced onions in butter over medium heat for 50-60 minutes until deep brown. Stir in garlic and flour, add white wine, 1.5 litres of beef stock and thyme, and simmer for 25 minutes. Ladle into oven-safe bowls, top with toasted baguette and grated Gruyère, and broil for 3-5 minutes until bubbling.
- Total time
- 1 hr 55 mins
- Calories
- 450 per serving
- Protein
- 18 g
- Yield
- 6 servings
- Difficulty
- Easy
- Method
- Simmering
Ingredients
Soup
Topping
Equipment
Large heavy-bottomed pot or Dutch oven (5-6 L) · 6 oven-safe soup bowls or crocks · Rimmed baking sheet · Box grater · Ladle
Quick Directions
Soften the onions
Cook the onions in butter, covered, for 10 minutes to soften.
Caramelize the onions
Cook uncovered for 40-50 minutes, stirring often, until deep golden brown.
Add garlic, flour and wine
Stir in garlic and flour, then deglaze with the wine.
Simmer the soup
Add stock and herbs and simmer for 25 minutes, then season.
Toast the bread
Bake the baguette slices at 200°C (400°F) until dry and crisp.
Top and broil
Ladle into oven-safe bowls, top with toasts and cheese, and broil for 3-5 minutes.
Serve with care
Move the hot bowls onto plates and rest for 2 minutes before serving.
Step-by-Step Instructions
Follow these detailed steps to make the perfect french onion soup.
Soften the onions
Melt the butter with the olive oil in a large heavy pot over medium heat. Add the onions and salt and stir to coat. Cover and cook for 10 minutes, stirring once or twice, until the onions have softened and released their liquid.
Caramelize the onions
Uncover and keep cooking for 40-50 minutes, stirring every few minutes, until the onions are soft, jammy and a deep golden brown. Stir in the sugar after the first 15 minutes if using. Turn the heat down to medium-low if they start to catch, and whenever a brown layer builds up on the bottom of the pot, add 2 tbsp water and scrape it up.
Add garlic, flour and wine
Stir in the garlic and cook for 1 minute, then sprinkle over the flour and stir for 1 minute more. Pour in the wine and scrape the bottom of the pot well. Let it bubble for 2 minutes until mostly evaporated.
Simmer the soup
Add the beef stock, thyme, bay leaf and pepper. Bring to a boil, then lower the heat and simmer uncovered for 25 minutes. Remove the thyme stems and bay leaf and season with more salt to taste.
Toast the bread
While the soup simmers, heat the oven to 200°C (400°F). Lay the baguette slices on the baking sheet and bake for 8-10 minutes, turning once, until dry and lightly golden. Switch the oven to broil and move a rack to about 15 cm below the element.
Top and broil
Set the oven-safe bowls on the baking sheet and ladle in the hot soup. Float 2 toasts on each bowl and pile the Gruyère on top, letting some fall over the edges. Broil for 3-5 minutes, watching closely, until the cheese is melted, bubbling and browned in spots.
Serve with care
Use oven mitts to move the bowls onto plates, since they will be extremely hot. Let the soup stand for 2 minutes before serving.
Recipe Tips
- Don't rush the onions. High heat browns the outside before they soften and can make them bitter, while medium heat and regular stirring give a sweet, deep flavour.
- The brown layer that forms on the bottom of the pot is where much of the flavour comes from. Scrape it up with a splash of water every time it builds up.
- With so few ingredients, the stock matters. Use a rich low-sodium beef stock and add salt only at the end, after the soup has simmered.
- Toast the bread until it is fully dry so it holds together in the soup instead of turning to mush.
- No oven-safe bowls? Top the toasts with cheese on the baking sheet, broil them until bubbling, then float them on bowls of hot soup.
Variations
- Vegetarian: use a rich mushroom or vegetable stock with 1 tbsp soy sauce for extra depth, and choose a cheese made without animal rennet.
- Use dry sherry instead of white wine, or add 2 tbsp brandy with the stock for a deeper, slightly sweet finish.
- Mix the cheeses: half Gruyère and half Emmental or Swiss gives a milder, stretchier topping.
- Gluten-free: skip the flour (the soup will be a little thinner) and use gluten-free bread for the toasts. Check that the stock is gluten-free.
Nutrition (per serving)
| Calories | 450 |
|---|---|
| Protein | 18 g |
| Carbs | 45 g |
| Fat | 21 g |
| Saturated fat | 12 g |
| Fibre | 5 g |
| Sugar | 12 g |
| Sodium | 1250 mg |
Estimated from the listed ingredients; values vary by brand.
Related Recipes
Storing & Reheating
- Fridge
- Refrigerate the soup without the bread or cheese in an airtight container for up to 4 days.
- Freezer
- Freeze the soup base for up to 3 months. Thaw it overnight in the fridge and add fresh toasts and cheese when you serve it.
- Reheat
- Bring the soup back to a simmer on the stove, then ladle it into oven-safe bowls, add toasts and cheese, and broil as in the recipe.
French Onion Soup FAQs
What are the best onions for French onion soup?
Yellow onions are the best all-round choice because they turn sweet and deeply brown while keeping some body. Sweet onions also work but make a sweeter soup, and a mix of yellow and red onions is fine too.
Why does it take so long to caramelize onions?
The onions first have to lose most of their water before their natural sugars can brown, and that browning has to happen slowly so it doesn't burn. Expect 50-60 minutes over medium heat for 1.5 kg of onions. Turning up the heat only scorches the outside.
What cheese goes on French onion soup?
Gruyère is the classic choice because it melts smoothly and browns well under the broiler with a nutty flavour. Comté, Emmental or Swiss cheese are good substitutes, alone or mixed with Gruyère.
Can I make French onion soup ahead of time?
Yes. The soup base keeps for up to 4 days in the fridge or 3 months in the freezer, and the flavour gets better after a day. Reheat it to a simmer, then add the toasts and cheese and broil just before serving.
Can French onion soup be made vegetarian?
Yes. Replace the beef stock with a rich mushroom or vegetable stock and add 1 tbsp soy sauce for savoury depth. Many hard cheeses use animal rennet, so pick a cheese labelled vegetarian.
Disclaimer
- Nutrition information is an estimate based on the listed ingredients. It changes with the brands, portion sizes and swaps you use.
- Read ingredient labels for allergens and for diet claims such as gluten-free or vegan. Products and their ingredients can change.
- Cooking times are a guide, since ovens, air fryers and slow cookers all run differently. Use a food thermometer and cook meat, poultry and fish to the safe internal temperatures in government food safety guidance.
- This recipe is general information, not medical or nutrition advice. If you have an allergy, a health condition or a special diet, check with a qualified health professional.
