French Soup Supplier: Classic French Onion Soup Recipe

French onion soup is a classic French dish of slowly browned onions simmered in savory stock, served beneath toasted baguette and bubbling Gruyère. The long, gentle cooking turns simple ingredients into a rich, sweet-and-savory soup, and the bread-and-cheese topping makes each bowl feel like a meal.

Ingredients

3 lb (1.36 kg) yellow onions, peeled and thinly sliced
4 tbsp (57 g) unsalted butter
1 tbsp (15 ml) olive oil
1 tsp (6 g) fine salt, plus more to taste
½ tsp (2 g) granulated sugar, optional, to help the onions brown evenly
2 tbsp (16 g) all-purpose flour
½ cup (120 ml) dry white wine
8 cups (1.9 L) beef stock, preferably low-sodium
1 tsp (1 g) fresh thyme leaves, or ½ tsp (0.5 g) dried thyme
1 (0.2 g) dried bay leaf
½ tsp (1 g) freshly ground black pepper
12 oz (340 g) baguette, cut into 12 slices about ½ inch (1.3 cm) thick
2 cups (200 g) coarsely grated Gruyère cheese

Instructions

Slice the onions and get everything ready. Peel and halve the onions, then slice them thinly from root to tip. Thin, even slices soften and brown at a similar pace. Measure the stock and wine, grate the cheese, and set out six oven-safe soup crocks that are rated for broiler use. If you do not have broiler-safe crocks, plan to toast the baguette and melt the cheese separately, then add them to the bowls.
Brown the onions slowly, about 45 minutes. Melt the butter with the olive oil in a large, heavy pot or Dutch oven over medium heat. Add the onions, salt, and optional sugar, and toss to coat. Cook, stirring every few minutes, until the onions become very soft and deeply golden brown. If they start sticking or the pot develops dark patches before the onions are tender, lower the heat and stir in a tablespoon of water. Avoid rushing this step with high heat: onions that scorch can make the soup bitter, while properly browned onions give it its characteristic depth.
Add the flour and wine, about 5 minutes. Sprinkle the flour over the onions and stir for 1 minute so no dry pockets remain. Pour in the wine, scraping the bottom of the pot with a wooden spoon to loosen the browned bits. Let it bubble for 3 to 4 minutes, until its sharp aroma softens. For a no-alcohol version, use extra stock here and add 1 teaspoon of wine vinegar or lemon juice near the end of cooking; the soup will have less wine aroma but will still taste balanced.
Simmer the soup, about 25 minutes. Stir in the beef stock, thyme, bay leaf, and black pepper. Bring the soup just to a boil, then reduce the heat to maintain a gentle simmer. Cook uncovered for 25 minutes, stirring once or twice. Remove the bay leaf, taste, and adjust the salt and pepper. If the soup tastes too sweet, a small splash of wine vinegar can sharpen it; if it tastes too salty, add a little water or unsalted stock.
Toast the baguette, about 8 minutes. While the soup simmers, heat the oven to 400°F (200°C). Arrange the baguette slices in one layer on a baking sheet and toast for about 4 minutes per side, until dry and lightly golden. The toasts should be firm enough to support the cheese, but they do not need to be dark brown because they will go under the broiler too.
Top and broil, about 2 minutes. Set the oven to broil. Ladle hot soup into the broiler-safe crocks, leaving room at the top. Float one or two toasted baguette slices on each serving and cover them generously with Gruyère. Place the crocks on a sturdy baking sheet and broil, watching continuously, until the cheese is melted, bubbling, and spotted golden, usually about 2 minutes. Broilers vary, so do not rely on the clock alone. Use oven mitts and let the crocks stand for a few minutes before serving; they will be extremely hot.

Tips

Give the onions enough time. The most common disappointment is pale, barely softened onions. Keep the heat at medium or lower and stir regularly; deep golden color develops gradually. If the onions brown unevenly, reduce the heat and add a little water to lift the fond from the pot.
Choose a stock you enjoy drinking. Low-sodium beef stock gives you better control over seasoning as the soup reduces. If using regular salted stock, start with less added salt and adjust after simmering. For a vegetarian soup, use a full-bodied vegetable stock; it will be lighter and less meaty in flavor.
Gruyère is traditional in many versions, but it is not the only option. If it is hard to find, use Emmental, Comté, or a mix of Swiss cheese and a little Parmesan. These melt well, though their flavor will be milder or sharper than Gruyère. Avoid very fresh mozzarella alone because it can release water and will not give the same nutty, browned topping.
Keep the bread from disappearing into the soup. Toasting it first helps it hold its shape under the cheese. For a more intact crouton, serve the toast and cheese on top at the table rather than letting the bread sit in the pot.

Serving Suggestions

Serve the soup immediately after broiling, while the cheese is still molten and the broth is piping hot. Put each crock on a heatproof plate with a napkin or folded towel underneath, and warn diners that the bowl and topping are hot. A crisp green salad dressed with a simple mustard vinaigrette makes a refreshing contrast to the rich soup. A small plate of sliced radishes, cornichons, or lightly dressed bitter greens also works well, especially if the soup is the main course.

If you are serving it as a first course, use smaller portions and one baguette slice per bowl. For a fuller meal, offer extra toasted baguette on the side and let people add it as they eat. Keep any additional cheese at the table rather than adding it to the whole pot, so the soup remains easy to store and reheat.

Variations

Vegetarian onion soup: Replace the beef stock with a robust vegetable stock. A teaspoon of soy sauce or miso stirred into the finished broth can add savory depth, but taste before adding salt because both are salty. Use vegetarian Gruyère-style cheese if needed. The result will not have the same beefy character, but the browned onions and toasted topping still make a satisfying soup.

Without wine: Replace the ½ cup (120 ml) wine with the same amount of stock. After simmering, add up to 1 teaspoon (5 ml) wine vinegar or lemon juice, a little at a time, until the broth tastes lively rather than sharp. Acid is best adjusted at the end because different stocks vary in saltiness and tang.

With garlic: For a gentle garlic note, rub the toasted baguette with the cut side of a halved garlic clove before topping it. This adds fragrance without changing the onion broth. You can also stir 1 minced garlic clove (about 3 g) into the onions during their final 2 minutes of browning; adding it earlier may cause it to burn during the long caramelizing step.

Make it without broiler-safe crocks: Ladle the soup into regular bowls, top with toasted baguette and grated cheese, then place the bowls on a baking sheet in a hot oven until the cheese melts. This will not brown as quickly or as dramatically as a broiler, so watch closely and use only bowls labeled oven-safe. Alternatively, melt the cheese on the toasts under the broiler and float each finished toast on a bowl of soup.

Storage and Reheating

For the best texture, store the soup and toasted bread separately. Cool the soup promptly and refrigerate it within 2 hours of cooking in a covered container. It keeps for 3 to 4 days in the refrigerator. The bread will soften if stored with the soup, so keep leftover baguette slices in an airtight container at room temperature for up to 2 days, or toast fresh slices when serving again.

Reheat soup gently in a saucepan over medium-low heat, stirring occasionally, until steaming throughout. If it has thickened, add a splash of water or stock. For food safety, leftovers should reach 165°F (74°C); check the center with a food thermometer. Assemble with fresh or re-crisped toast and cheese, then broil just before serving. Freeze the broth without bread or cheese for up to 3 months for best quality. Thaw overnight in the refrigerator and reheat to 165°F (74°C); the onions may soften further, but the flavor remains useful for a quick meal.

Frequently Asked Questions

Why are my onions not turning golden? They may need more time, or the pan may be crowded and too cool. Keep them in a wide, heavy pot and continue cooking, stirring every few minutes. If liquid collects, let it evaporate before expecting the onions to brown. Do not turn the heat very high to compensate, since the outside can scorch before the onions soften.

Can I make French onion soup ahead? Yes. Make the broth through the simmering step, cool it, and refrigerate it for up to 3 to 4 days. Reheat it to 165°F (74°C), then toast the bread, add the cheese, and broil just before serving. Keeping the topping separate prevents soggy bread and makes the soup easier to store.

Can I use chicken stock instead of beef stock? Yes. Chicken stock makes a lighter soup and lets the caramelized onions stand out more clearly. Use unsalted or low-sodium stock if possible and adjust the seasoning after simmering. Vegetable stock also works, though the broth will be less robust than the classic beef-stock version.

What can I use instead of Gruyère? Emmental, Comté, or Swiss cheese are good melting substitutes. A little Parmesan mixed into one of them adds a saltier, more savory edge. Use a cheese that melts smoothly and has enough flavor to stand up to the onions; very mild cheeses can taste bland against the broth.

How do I keep the bread from getting soggy? Toast the baguette until it is dry and lightly crisp, and assemble each bowl just before broiling. The bread will soften somewhat as it absorbs broth, which is part of the dish, but a firm toast holds up longer. If you prefer distinct crunchy pieces, serve the cheesy toast on the side and dip it as you eat.

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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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