Classic French Onion Soup with Gruyère Croutons (Make-Ahead Onions)
Deeply caramelized onions simmered with white wine, thyme and rich beef broth, then crowned with toasted baguette and bubbling broiled Gruyère. A step-by-step, no-shortcut-to-flavor French onion soup with tips for perfectly browned (never burnt) onions, a make-ahead plan, and a no-crock option.
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Ingredients
Serves 6
- 4 tbsp unsalted butter
- 1 tbsp olive oil
- 3 lb yellow onionsabout 5 large, halved and thinly sliced pole to pole
- 1 tsp kosher saltplus more to taste
- 1/2 tsp granulated sugaroptional, helps browning
- 3 cloves garlicminced
- 2 tbsp all-purpose flour
- 3/4 cup dry white wineor dry sherry
- 6 cups low-sodium beef broth
- 4 sprigs fresh thymeor 1 tsp dried thyme
- 1 bay leaf
- 1 tsp Worcestershire sauce
- 1/2 tsp freshly ground black pepper
- 12 slices baguettecut 3/4 inch thick
- 8 oz Gruyère cheeseshredded, about 2 cups
- 1/4 cup Parmesan cheesefinely grated
The method
Melt the butter with the olive oil in a large Dutch oven over medium heat. Add the sliced onions, salt and sugar (if using) and toss to coat. Cover and cook for 10 minutes, stirring once or twice, until the onions are soft and have released their liquid.
10 minUncover and reduce the heat to medium-low. Cook, stirring and scraping the bottom every 4 to 5 minutes, until the onions are deep golden brown, jammy and reduced to about 2 cups, 45 to 55 minutes. Whenever the browned layer on the bottom of the pot looks dark, add 2 tablespoons of water and scrape it up. Lower the heat if the onions start to scorch.
50 minStir in the garlic and cook for 1 minute until fragrant. Sprinkle in the flour and stir constantly for 1 minute to cook off the raw taste.
2 minPour in the wine and scrape the bottom of the pot clean. Simmer for about 3 minutes, until the wine is reduced by half.
3 minAdd the beef broth, thyme, bay leaf, Worcestershire sauce and pepper. Bring to a boil, then reduce the heat and simmer gently, uncovered, for 25 minutes. Discard the thyme stems and bay leaf, then taste and add salt as needed.
25 minWhile the soup simmers, heat the oven to 400°F. Arrange the baguette slices on a baking sheet and toast for 8 to 10 minutes, flipping halfway, until dry and crisp all the way through.
10 minSwitch the oven to broil with a rack about 6 inches from the heat. Set 6 oven-safe soup crocks on a rimmed baking sheet and ladle in the hot soup. Float 2 toasts on each, then pile on the Gruyère and sprinkle with Parmesan, letting some cheese hang over the edges.
4 minBroil for 3 to 5 minutes, watching closely, until the cheese is melted, bubbling and browned in spots. Let the crocks rest for 2 minutes before serving; they will be very hot.
6 min
Timings are a guide. Use the instruction and your own judgment as you cook.
Why this works
The whole flavor of French onion soup comes from patience with the onions. A short covered sweat softens them and draws out moisture, so they brown evenly instead of frying at the edges. Deglazing with a splash of water whenever the bottom of the pot darkens folds that browned flavor back into the onions and keeps them from turning bitter. Low-sodium broth lets the onions be the star and keeps the soup from getting too salty once the cheese goes on.
Make ahead
- Onions: Caramelize them up to 3 days ahead and refrigerate. On soup night, you’re about 35 minutes from dinner.
- Soup: Make it through step 5, cool, and refrigerate for up to 4 days or freeze for up to 3 months. Freeze it without bread or cheese, then reheat and finish under the broiler.
- Toasts: Toast the baguette a day ahead and keep it in an airtight container.
No soup crocks?
Top the toasted baguette slices with the cheese on the baking sheet and broil for 2 to 3 minutes. Ladle the soup into regular bowls and float the cheesy toasts on top.
Swaps
- Vegetarian: Use a rich mushroom or vegetable broth and swap the Worcestershire for 1 tablespoon soy sauce or 2 teaspoons white miso (many Worcestershire sauces contain anchovy).
- No wine: Use an extra 3/4 cup broth plus 1 teaspoon sherry vinegar or apple cider vinegar.
- Cheese: Swiss, Comté, or a mix of Gruyère and provolone all melt beautifully.
Fewer tears
Chill the onions for 30 minutes before slicing and use your sharpest knife. A dull blade crushes more cells and releases more of the compound that makes you cry.
Photo: “Mmm…onion soup” by jeffreyw, via Wikimedia Commons, licensed CC BY 2.0.
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