One-Pot Sourdough French Onion Soup with Cheese Croutons

Name: One-Pot Sourdough French Onion Soup with Cheese Croutons
Prep time: 20 min
Cook time: 1 h 5 min
Total time: 1 h 25 min
Yield: 4 servings
Cuisine: French
Ingredients: 3 lbs (1360 g) yellow onions, peeled, halved lengthwise, thinly sliced; 3 tablespoons (43 g) unsalted butter; 1 tablespoon (15 ml) extra-virgin olive oil; ½ cup (120 ml) dry white wine or brandy; 6 cups (1440 ml) beef broth (homemade or low-sodium store-bought); 1 bay leaf; 2 sprigs fresh thyme; kosher salt, to taste; freshly ground black pepper, to taste; 4 oz (115 g) sourdough bread, cut into ½-inch (1.3 cm) slices, then torn or cut into rough 1-inch (2.5 cm) cubes; 4 oz (115 g) Gruyère cheese, coarsely grated or thinly sliced; 1½ tablespoons (21 g) unsalted butter, melted; ¼ teaspoon (½ g) garlic powder

From the MyKitchenBank Kitchen

A rustic, warming French onion soup made entirely in one pot, built on deeply caramelized onions, rich beef broth, and a splash of dry white wine or brandy. Topped with crispy sourdough croutons and melted Gruyère cheese. This classic soup is comforting, elegant, and perfect for cool-weather dinners.

Prep: 20 min
Cook: 1 hr 5 min
Wait: 5 min
Total: 1 hr 30 min
Makes: 4 bowls (about 10 oz / 280 ml each)

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Ingredients

4 servings

3 lbs (1360 g) yellow onions, peeled, halved lengthwise, thinly sliced
3 tablespoons (43 g) unsalted butter
1 tablespoon (15 ml) extra-virgin olive oil
½ cup (120 ml) dry white wine or brandy
6 cups (1440 ml) beef broth (homemade or low-sodium store-bought)
1 bay leaf
2 sprigs fresh thyme
kosher salt, to taste
freshly ground black pepper, to taste
For the cheese croutons
4 oz (115 g) sourdough bread, cut into ½-inch (1.3 cm) slices, then torn or cut into rough 1-inch (2.5 cm) cubes
4 oz (115 g) Gruyère cheese, coarsely grated or thinly sliced
1½ tablespoons (21 g) unsalted butter, melted
¼ teaspoon (0.5 g) garlic powder

Equipment (7)

Large heavy-bottomed pot or Dutch oven (5–6 quart / 4.7–5.7 L)
Wooden spoon or heat-resistant spatula
Measuring cups and spoons
Sharp chef's knife
Cutting board
Small baking sheet or toaster oven rack
Ladle

Steps

Before you start

Cut onions into thin, even slices so they caramelize uniformly.
Have beef broth warmed in a separate pot or kettle to speed cooking.
Slice and toast croutons ahead if you like; reheat them just before serving.
Use a heavy-bottomed pot (Dutch oven or large stockpot) to prevent scorching.

1
Prep ingredients and toast croutonsOven 375°F / 190°C
- Toss sourdough bread cubes with melted butter and garlic powder in a small bowl.
- Spread on a baking sheet in a single layer.
- Toast in a 375°F (190°C) oven for 8–10 minutes, stirring once halfway through, until they are golden and crispy on the outside but still slightly chewy inside.
- Set aside to cool.
- (You can do this while the onions cook, or prepare them up to 2 hours ahead and store in an airtight container at room temperature.)
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Ready when: Croutons are golden and crispy on the outside
Tip: Don't walk away; they can burn quickly once they start browning.
2
Start caramelizing onions
- Heat butter and olive oil in a large heavy-bottomed pot (5–6 quart / 4.7–5.7 L) over medium heat until the butter is foaming.
- Add all the sliced onions and stir well to coat them evenly.
- Cook uncovered, stirring every 3–4 minutes, for about 15–20 minutes.
- The onions will release water and steam, but they'll gradually soften and begin to turn golden.
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Ready when: Onions are softened and beginning to turn light golden, with no liquid pooling in the pot
Tip: Stir regularly to prevent sticking and ensure even browning. If they're sticking, lower heat slightly and add a splash of water.
3
Continue caramelizing until deep golden
- Reduce heat to medium-low and continue cooking, stirring every 4–5 minutes, for another 25–30 minutes.
- The onions will slowly turn a rich, deep golden brown and become very soft and almost jam-like.
- You may see a thin brown crust forming on the bottom of the pot—this is flavorful fond, not burning.
- Scrape it up with your spoon and stir it back into the onions.
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Ready when: Onions are deep golden or light brown, very soft, and have released all their liquid; the pot looks glossy and concentrated
Tip: Patience is key here. Rushing this step by raising heat will scorch them instead of caramelizing them sweetly. The whole process takes 40–50 minutes total.
4
Deglaze with wine
- Pour in the dry white wine or brandy and scrape the bottom of the pot vigorously with a wooden spoon to lift up all the brown fond.
- Stir well and let the wine simmer uncovered for 2–3 minutes to cook off most of the alcohol and reduce slightly.
- The pot will smell rich and savory.
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Ready when: Liquid is reduced by about half and the smell of raw alcohol has faded
Tip: Don't skip the deglazing—all that fond on the bottom is concentrated flavor that belongs in your soup.
5
Add broth and herbs
- Pour in the warm beef broth, then add the bay leaf and thyme sprigs.
- Stir well to combine everything.
- Increase heat to medium and bring the soup to a gentle simmer.
- Once simmering, reduce heat to medium-low and let it bubble gently, uncovered, for 15–20 minutes.
- This allows the flavors to meld and the soup to concentrate slightly.
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Ready when: Soup is at a gentle, rolling simmer; flavors have deepened and melded
Tip: Use a warm broth if you have it—it will bring the soup to temperature faster and won't cool down the pot.
6
Season to taste
- Remove the bay leaf and thyme sprigs using tongs or a slotted spoon.
- Taste the soup and season generously with kosher salt and freshly ground black pepper.
- Start with ½ teaspoon of salt and adjust from there—remember that the Gruyère cheese will add more saltiness, so don't over-salt now.
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Ready when: Herbs are removed and soup is well seasoned, with no bitter or flat taste
Tip: Always taste before serving; salt levels vary widely depending on your broth and personal preference.
7
Assemble and serve
- Ladle the hot soup into four serving bowls, filling each about three-quarters full (about 9–10 oz / 250–280 ml of broth and onions per bowl).
- Top each bowl with a handful of warm toasted croutons (about 5–6 pieces per bowl) and then sprinkle a generous handful of grated Gruyère cheese over the top (about 1 oz / 28 g per bowl).
- The hot soup will begin to melt the cheese and soften the croutons slightly.
- Serve immediately.
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Ready when: Soup is piping hot, cheese is beginning to melt, and croutons are warmed through
Tip: If your croutons have cooled, you can briefly warm them in the oven or toast them in a skillet just before serving.

Good to know

Tips

Caramelizing onions takes 45–50 minutes total, not 15—patience is essential. Low, steady heat builds deep, sweet flavor far better than high heat.
Save the fond (brown crust) on the pot bottom. It's umami-rich and should be scraped up and incorporated into the soup, not discarded.
For extra richness, stir 2 tablespoons of good cognac or brandy into the finished soup just before serving, or add a dollop of crème fraîche to each bowl.
If you prefer a thicker, more stewlike consistency, simmer the soup uncovered for an extra 10–15 minutes to reduce the broth further.

Make ahead

You can caramelize the onions and simmer the broth up to 2 days ahead; cool, cover, and refrigerate. Reheat gently over medium-low heat on the stovetop until steaming. Toast the croutons up to 2 hours ahead and store in an airtight container at room temperature. Assemble and serve fresh.

Storage & reheating

Refrigerate the soup (without croutons and cheese) in an airtight container for up to 4 days. Reheat on the stovetop over medium-low heat, stirring occasionally, until warmed through. Do not freeze; the texture of the broth may become cloudy upon thawing. Croutons keep in an airtight container at room temperature for up to 2 days.

Substitutions

Gruyère cheese → Swiss cheese or Emmental. Both melt smoothly and have a mild, nutty flavor similar to Gruyère. Use the same amount.
dry white wine or brandy → brandy, cognac, or dry sherry (use the same amount); or omit and use ½ cup additional beef broth. Each adds a different depth of flavor. If omitting, the soup will be slightly less complex but still delicious.
sourdough bread → crusty baguette or ciabatta. Any sturdy bread will work. Sourdough's tangy flavor is lovely with the sweet onions, but these alternatives are equally good.
fresh thyme → 1 teaspoon dried thyme. Use one-third the amount of dried herbs. Add it directly to the broth without removing before serving, or tie it in a sachet so it's easy to fish out.