A deeply flavorful, slow-cooked onion soup with a rich, savory broth, topped with crisp toasted baguette slices and bubbling golden Gruyère cheese—this Classic French Onion Soup brings elegance and comfort in every spoonful. Perfect for a chilly evening or as a sophisticated starter, it’s a timeless dish that never fails to impress.

Why You’ll Love This Recipe

• Rich, caramelized flavor: Slow-cooked onions develop a deep, sweet-savory flavor that defines this dish.
• Cheesy, crusty topping: Golden Gruyère and Parmesan atop toasted baguette provide a satisfying, melty finish.
• Elegant yet comforting: A rustic French bistro classic that feels both refined and soul-warming.
• Customizable broth options: Choose between beef or vegetable broth for a traditional or vegetarian version.
• Perfect for entertaining: Serve in oven-safe bowls for a dramatic and delicious presentation.

Ingredients

(Tip: You can find the complete list of ingredients and their measurements in the recipe card below.)

For the Soup:

• yellow onions, thinly sliced
• unsalted butter
• olive oil
• sugar
• salt
• garlic, minced
• dry white wine (optional)
• beef or vegetable broth
• fresh thyme (or dried)
• all-purpose flour
• black pepper

For the Topping:

• baguette, sliced into ½-inch rounds
• shredded Gruyère cheese
• grated Parmesan (optional)

Directions

1. In a large heavy-bottomed pot or Dutch oven, melt the butter with olive oil over medium heat.
2. Add the sliced onions, sugar, and salt. Cook slowly, stirring often, for 30–40 minutes until onions are deeply golden and caramelized.
3. Stir in minced garlic and cook for 1 additional minute.
4. Sprinkle in the flour and stir continuously for 1–2 minutes to eliminate the raw flour taste.
5. Pour in the white wine, if using, and deglaze the pot by scraping up any browned bits from the bottom.
6. Add the broth and thyme. Bring the soup to a gentle simmer and cook uncovered for 20–25 minutes to deepen the flavor. Season with salt and pepper to taste.
7. While the soup simmers, toast the baguette slices until crisp and lightly golden.
8. Preheat your oven’s broiler.
9. Ladle the hot soup into oven-safe bowls. Place one or two toasted baguette slices on top of each bowl.
10. Sprinkle generously with shredded Gruyère and Parmesan, if using.
11. Place the bowls on a baking tray and broil for 2–3 minutes, or until the cheese is melted and bubbly.
12. Serve immediately, garnished with fresh thyme if desired.

Servings and timing

Servings: Serves 4–6
Prep time: 15 minutes
Cook time: 1 hour 10 minutes
Total time: About 1 hour 25 minutes

Variations

• Vegetarian version: Use high-quality vegetable broth and skip the Parmesan or use a vegetarian alternative.
• Vegan option: Use plant-based butter, vegetable broth, and vegan cheese substitutes.
• No wine: Simply omit the white wine and replace with an equal amount of broth.
• Add a splash of brandy: For a richer, more traditional finish, stir in a tablespoon of cognac or brandy just before serving.
• Use different cheeses: Comté, Emmental, or Swiss cheese work well in place of Gruyère.

Storage/Reheating

• Refrigeration: Store leftover soup (without bread and cheese) in an airtight container for up to 4 days.
• Freezing: Soup freezes well without the bread topping. Freeze in portions for up to 2 months.
• Reheating: Reheat on the stove over medium heat until hot. Toast fresh bread and add cheese before serving.
• Assembly tip: Always add the bread and cheese topping fresh just before serving for best texture.

FAQs

What onions are best for French onion soup?

Yellow onions are ideal due to their balanced sweetness and flavor. You may also use a mix of yellow and sweet onions for extra depth.

Can I make this soup without wine?

Yes. The wine adds acidity and complexity, but it’s not essential. Replace it with extra broth or a splash of balsamic vinegar.

How do I prevent the onions from burning?

Cook low and slow, stirring frequently. Adjust the heat as needed to avoid scorching while allowing proper caramelization.

Why do we add sugar to the onions?

A small amount of sugar accelerates caramelization and enhances the natural sweetness of the onions.

Can I prepare the soup in advance?

Yes, the soup base can be made 1–2 days ahead and reheated. Add fresh bread and cheese before broiling and serving.

Is Gruyère cheese necessary?

Gruyère is traditional and melts beautifully, but other melting cheeses like Swiss, Emmental, or even mozzarella can be substituted.

What type of broth should I use?

Beef broth is classic for depth and richness. Vegetable broth makes the dish suitable for vegetarians and still tastes excellent.

Do I need oven-safe bowls?

Yes, for broiling the cheese. If unavailable, broil the cheese-topped bread separately and place on the soup just before serving.

Can I use store-bought croutons?

For a shortcut, yes. Use large croutons or baguette slices topped with cheese and broiled separately.

What should I serve with French onion soup?

It can stand alone as a meal or pair beautifully with a simple green salad, roasted vegetables, or a light quiche.

Conclusion

Classic French Onion Soup offers a deeply satisfying experience with its rich broth, tender caramelized onions, and a bubbling cheese crust. Whether you’re serving it as an elegant starter or a warming main course, this timeless French dish is the epitome of comfort and sophistication. With basic ingredients and a bit of patience, you can bring the taste of a French bistro into your own kitchen.

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