Delia Smith French Onion Soup Recipe for a Cozy Supper

French onion soup is a French classic of slowly browned onions simmered in savory broth, served beneath toasted bread and melted cheese. This home-style recipe uses patient stovetop cooking for deep flavor and a bubbling Gruyère topping; it is a practical classic-style version, not a transcription of a particular cookbook recipe.

Ingredients

3 lb yellow onions (1.36 kg), peeled and thinly sliced
3 tbsp unsalted butter (42 g)
1 tbsp olive oil (15 ml)
1 tsp granulated sugar (4 g), optional
1 tsp fine salt (6 g), plus more to taste
2 tbsp all-purpose flour (16 g)
½ cup dry white wine (120 ml), or use additional broth
8 cups beef broth (1.9 L), preferably low-sodium; vegetable broth also works
2 bay leaves
4 fresh thyme sprigs (about 2 g), or ½ tsp dried thyme (1 g)
½ tsp freshly ground black pepper (1 g)
1 baguette, about 8 oz (225 g), cut into 8 slices about ½ inch (1.3 cm) thick
2 cups grated Gruyère cheese (200 g)

Instructions

Prepare the onions and equipment. Peel the onions, cut them in half from root to tip, and slice them thinly and evenly. Set a heavy 5- to 6-quart (4.7- to 5.7-L) pot or Dutch oven over medium-low heat. Have an oven-safe soup bowl for each serving ready for the final topping. If you do not have oven-safe bowls, the soup can be served with the cheese toast on the side instead.
Soften the onions. Add the butter and olive oil to the pot. Once the butter has melted, add the onions, sugar if using, and salt. Stir well, cover, and cook for 10 minutes, stirring once halfway through. The onions should soften and release moisture, not fry or take on dark color at this stage. If they begin sticking, lower the heat slightly.
Brown them slowly. Remove the lid and cook the onions uncovered for 35 minutes, stirring every few minutes and more often near the end. Scrape the bottom of the pot as you stir. The onions should become very soft and turn a deep golden brown, with no burnt black patches. If the fond on the bottom threatens to scorch, add a tablespoon of water and scrape it loose. Slow browning builds the soup’s characteristic sweetness; turning the heat up to rush it can leave the onions bitter.
Add flour and wine. Sprinkle the flour over the onions and stir continuously for 1 minute so it cooks through and coats them evenly. Pour in the white wine and scrape the base of the pot to release the browned bits. Let it bubble for 2 minutes, until the sharp alcohol smell has eased. If you are leaving out wine, use a splash of broth to deglaze the pot instead.
Simmer the soup. Add the broth, bay leaves, thyme, and black pepper. Bring the liquid to a gentle simmer, then reduce the heat so it bubbles lightly rather than boils hard. Simmer uncovered for 25 minutes. Remove the bay leaves and thyme stems, taste, and adjust the salt and pepper. Broth varies in saltiness, so make the final adjustment only after the soup has simmered.
Toast the baguette. While the soup simmers, heat the oven to 400°F (200°C). Arrange the baguette slices in one layer on a baking sheet and bake for 8 minutes, turning them once if one side is browning faster. They should be dry and lightly golden, sturdy enough to sit on the soup without immediately collapsing. Keep an eye on thin slices, which can toast sooner.
Top and melt the cheese. Set an oven rack so the tops of the bowls will sit several inches below the broiler. Ladle the hot soup into four oven-safe bowls placed on a rimmed baking sheet. Float two toast slices on each bowl and divide the Gruyère over the bread. Broil for about 3 minutes, watching continuously, until the cheese is bubbling and browned in spots. Broilers vary, so remove the bowls as soon as the cheese looks right. Use oven mitts and serve on heatproof plates.
Serve carefully. The bowls and soup will be extremely hot. Let them stand for a minute or two on the table before eating, and warn everyone that the cheese-covered surface holds heat. If using ordinary bowls, put the cheese on the toasted baguette slices and serve them alongside the soup rather than putting the bowls under the broiler.

Tips

Slice evenly. Similar-size onion slices soften at roughly the same rate. A mandoline can help, but use its hand guard and stop before the onion gets too small to hold securely.
Give the onions time. Their color should develop gradually over the full 45-minute uncovered cooking period. If the pot is too hot, the outside can burn while the center remains firm; turn the heat down and stir more often rather than adding extra sugar to compensate.
Choose broth thoughtfully. Low-sodium beef broth gives a traditional savory base and lets you control seasoning. Vegetable broth makes the soup vegetarian if the wine is suitable and the cheese uses vegetarian rennet; it gives a lighter flavor. A rich, very salty broth may need little or no added salt.
Keep the toast crisp. Toast the bread until it is dry through the middle, not just colored on the surface. Fresh, soft bread can sink quickly. If you prefer a less messy bowl, serve the toast and cheese separately and dip them as you eat.

Serving Suggestions

Serve each bowl as a starter, or make it a simple main course with a green salad dressed in a sharp vinaigrette. The acidity of the dressing balances the soup’s sweet onions and rich cheese. A side of roasted vegetables or a small platter of sliced apples and crisp greens also works well without competing with the broth.

For a relaxed supper, bring the pot of soup and a basket of extra toasted baguette to the table, then add the cheese-topped toast to individual bowls. This is especially useful when diners have different preferences about how soft the bread should become. Set the bowls on heatproof mats and use a ladle, since the broth is hot and the topping can slide.

Variations

Wine-free: Omit the white wine and use an equal amount of broth to deglaze the onions. A teaspoon of cider vinegar stirred in at the end can add a little brightness, but start with less and taste; vinegar is sharper than wine and should not dominate.

Different cheese: Gruyère melts smoothly and has a nutty, savory flavor. Emmental or Swiss-style cheese is a good substitute, while a mix of mozzarella and Parmesan gives a stretchier, milder topping with a saltier finish. Avoid piling on too much cheese, which can make the top greasy and difficult to eat.

Vegetarian: Replace the beef broth with a well-flavored vegetable broth. Check that the cheese is made with vegetarian rennet if that matters to your diet. Since vegetable broth can taste less full-bodied, brown the onions carefully and taste the soup before serving; a small extra pinch of pepper or thyme may help round it out.

More substantial bowls: Use one larger slice of baguette per bowl and add a little more cheese if the soup is the main course. You can also offer extra toast at the table. Avoid adding uncooked bread directly to the pot, as it will soak up broth and turn soft before the soup is served.

Storage and Reheating

For the best texture, store the soup and toasted bread separately. Let the soup cool briefly, then refrigerate it within 2 hours of cooking in a covered container. It keeps for 3 to 4 days in the refrigerator. The bread is best toasted fresh, but leftover slices can be kept at room temperature in a dry, airtight container for about a day; humidity makes them soften.

Reheat only the amount of soup you need in a saucepan over medium heat, stirring occasionally until steaming hot throughout. USDA FSIS guidance is to reheat leftovers to 165°F (74°C); check the center with a food thermometer. Add a splash of broth or water if the soup has thickened. Toast fresh baguette, top with cheese, and broil just before serving rather than storing assembled bowls.

Freeze the soup without bread or cheese in a freezer-safe container for up to 2 to 3 months for best quality. Leave room for expansion, thaw it overnight in the refrigerator, then reheat to 165°F (74°C). The onions and broth may separate slightly after freezing, but stirring as the soup warms usually brings the texture back together.

Frequently Asked Questions

Why are my onions not turning brown?

They may be releasing water faster than it can evaporate, especially if the pot is crowded or the heat is very low. Keep the pot uncovered after the first 10 minutes, stir regularly, and allow the full cooking time. If liquid pools in the bottom, continue cooking until it evaporates. Do not raise the heat so much that the onions scorch.

Can I make French onion soup ahead?

Yes. Cook the soup through the simmering step, cool it promptly, and refrigerate it for up to 3 to 4 days. Reheat it to 165°F (74°C), then toast the bread and add the cheese immediately before serving. Keeping the topping separate prevents it from becoming soggy and makes the final broiling step quick.

Can I make it without oven-safe soup bowls?

Yes. Serve the soup in ordinary bowls and place the cheese-topped baguette under the broiler on a baking sheet until melted and browned. Set one or two pieces on each bowl at the table, or serve them on the side. Do not put regular ceramic or glass bowls under a broiler unless the manufacturer specifically says they are broiler-safe.

What can I use instead of Gruyère?

Emmental, Swiss-style cheese, or a blend of mozzarella and Parmesan can all work. Emmental is the closest in general texture and flavor; mozzarella melts readily but tastes milder, while Parmesan adds a saltier, more pronounced note. Grate the cheese yourself if possible, since pre-grated cheese may melt less smoothly.

Is French onion soup vegetarian?

Not when it is made with beef broth. Use vegetable broth instead and check the cheese label if you avoid animal rennet. The soup will taste somewhat lighter, but slow-browned onions, thyme, and a well-seasoned broth still give it plenty of savory character.

Can I use red onions or sweet onions?

Yellow onions are a dependable choice because their flavor becomes mellow and savory as they cook. Red onions can be used, though the finished soup may be darker and slightly fruitier. Sweet onions also work, but they can taste noticeably sweeter, so omit the optional sugar and taste before adding any extra seasoning.

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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

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