Classic French Onion Soup Recipe

Name: Classic French Onion Soup Recipe
Prep time: 20 min
Cook time: 75 min
Total time: 95 min
Yield: 6 servings
Ingredients: 4 tbsp unsalted butter; 2 tbsp olive oil; 4 large large yellow onions, thinly sliced; 1 tsp granulated sugar; 1 tsp kosher salt; 2 tbsp all-purpose flour; 1/2 cup dry white wine; 8 cups beef broth; 2 leaves bay leaves; 4 sprigs fresh thyme sprigs; 12 slices baguette slices, 1-inch thick; 2 cups gruyere cheese, shredded

A crock of French onion soup topped with a toasted baguette slice and bubbling, browned gruyere cheese, set on a wooden table. — Photo by sheri silver on Unsplash

Slowly caramelizing the onions for close to an hour builds the deep, sweet-savory flavor that makes this soup taste rich, without needing anything more exotic than onions, broth, butter, and wine. Broiling the cheese-topped bread directly on the soup melts and browns the gruyere while keeping the bread from turning soggy.

Prep: 20 min
Cook: 1 hr 15 min
Total: 1 hr 35 min
Servings: 6

Ingredients

Servings6

Dietary goal:

4 tbsp unsalted butter
2 tbsp olive oil
4 large large yellow onions, thinly sliced
1 tsp granulated sugar
1 tsp kosher salt
2 tbsp all-purpose flour
1/2 cup dry white wine
8 cups beef broth
2 leaves bay leaves
4 sprigs fresh thyme sprigs
12 slices baguette slices, 1-inch thick
2 cups gruyere cheese, shredded

Nutrition per serving

Calories: 540
Protein: 21g
Carbs: 53g
Fat: 26g

Based on the recipe as written, one serving. Recalculates if you swap an ingredient above. An estimate only, exact values depend on the specific ingredients used.

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Instructions

1Melt the butter with the olive oil in a large, heavy pot over medium heat.
2Add the sliced onions and salt, stir to coat, and cook uncovered, stirring every few minutes, until they soften and start to turn golden, about 15 minutes.
3Sprinkle in the sugar and reduce the heat to medium-low. Continue cooking, stirring every 5 minutes or so and scraping up any browned bits from the bottom of the pot, until the onions are deeply caramelized and a jammy, deep amber-brown color, 40 to 50 minutes total.
4Stir in the flour and cook for 1 minute, stirring constantly, until it coats the onions and no raw flour smell remains.
5Pour in the white wine, scraping the bottom of the pot to release any browned bits, and simmer for 2 to 3 minutes until slightly reduced.
6Add the beef broth, bay leaves, and thyme sprigs. Bring to a simmer, then reduce the heat and cook uncovered for 20 minutes to let the flavors meld. Remove the bay leaves and thyme stems, and season with salt and pepper to taste.
7While the soup simmers, arrange the baguette slices on a baking sheet and toast under the broiler for 1 to 2 minutes per side, until dry and lightly golden.
8Preheat the broiler. Ladle the soup into oven-safe crocks or bowls set on a sturdy baking sheet. Top each with one or two toasted baguette slices, then divide the shredded gruyere evenly over the top.
9Broil 4 to 6 inches from the heat for 2 to 4 minutes, watching closely, until the cheese is melted, bubbling, and browned in spots. Let cool for a few minutes before serving, the crocks will be very hot.

Tips & variations

A splash of brandy or cognac stirred in with the wine adds another layer of depth if it's on hand.
No oven-safe crocks? Toast the bread and melt the cheese under the broiler on a separate tray, then float the cheesy toast on top of the soup just before serving.
Comte or a mix of gruyere and mozzarella both work as substitutes if gruyere isn't available.
For a vegetarian version, swap the beef broth for a well-seasoned mushroom or vegetable stock; the caramelized onions still carry most of the flavor.

Storage & reheating

Store the soup base (without bread or cheese) in an airtight container in the refrigerator for up to 4 days, or freeze for up to 3 months. Reheat gently on the stovetop, then ladle into broiler-safe bowls and add fresh toasted bread and cheese before broiling again, previously melted cheese doesn't reheat well.

Tips from the Tulo kitchen

Slicing the onions pole to pole (top to bottom) rather than across the equator helps them hold their shape better as they slowly break down.
If the onions start sticking or scorching before they're fully caramelized, add a splash of water or broth to loosen the fond instead of turning up the heat.

FAQ

Why do the onions take so long to caramelize?

True caramelization is a slow breakdown of the onions' natural sugars, which only happens fully at low to medium-low heat; rushing it with high heat browns the surface before the onions soften and sweeten all the way through.

Can I use a slow cooker to caramelize the onions?

Yes, cooking sliced onions with butter on low for 8 to 10 hours produces a similar deep caramelization with far less stirring, though the flavor from the stovetop's browned fond is slightly more concentrated.

What can I use instead of gruyere?

Comte, Emmental, or a blend of gruyere and mozzarella all melt and brown well; pre-shredded cheese blends tend to melt less smoothly due to the anti-caking starch coating.

Can I make this soup ahead of time?

Yes, the onion and broth base actually improves after a day or two in the refrigerator as the flavors continue to meld; add the bread and cheese only right before serving and broiling.