Classic French Onion Soup with Gruyère Toasts

Name: Classic French Onion Soup with Gruyère Toasts
Prep time: 20 min
Cook time: 1 h 40 min
Total time: 2 h 5 min
Yield: 6 starter servings, each with 2 Gruyère toasts
Cuisine: French
Ingredients: 2 pounds 10 ounces (1.2 kg) yellow onions, weighed before peeling, about 6 large onions; 3 tablespoons (42 g) unsalted butter; 1 tablespoon (15 ml) olive oil; 1/2 teaspoon (3 g) fine sea salt; 2 garlic cloves, about 6 g, finely minced; 1/2 cup (120 ml) dry white wine, such as Sauvignon Blanc or unoaked Chardonnay; 6 cups (1.44 liters) low-sodium beef broth; 4 fresh thyme sprigs; 1 dried bay leaf; 1/4 teaspoon freshly ground black pepper; 2 tablespoons (30 ml) water at a time, only if needed to loosen browned bits during caramelization; 12 baguette slices, cut 1/2 inch (1.25 cm) thick, about 180 g total; 6.3 ounces (180 g) Gruyère cheese, freshly grated; 1 teaspoon fresh thyme leaves, optional, for garnish

Imperial November 8, 2026November 8, 2026

Quick Recipe Version (TL;DR)

Classic French Onion Soup with Gruyère Toasts is a warming Christmas starter with deeply caramelized onions, savory beef broth, and crisp baguette toasts tucked beneath bubbling golden cheese.

Yield: 6 starter servings, each with 2 Gruyère toasts
Prep Time: 20 minutes
Cook Time: 1 hour 40 minutes
Total Time: 2 hours 5 minutes, including 5 minutes cooling

Quick Ingredients

2 pounds 10 ounces (1.2 kg) yellow onions, thinly sliced
3 tablespoons (42 g) unsalted butter and 1 tablespoon (15 ml) olive oil
2 garlic cloves, minced
1/2 cup (120 ml) dry white wine
6 cups (1.44 liters) low-sodium beef broth
4 fresh thyme sprigs and 1 dried bay leaf
1/2 teaspoon (3 g) fine sea salt and 1/4 teaspoon ground black pepper
12 baguette slices, 1/2 inch (1.25 cm) thick, about 180 g total
6.3 ounces (180 g) Gruyère cheese, freshly grated
1 teaspoon fresh thyme leaves, optional, for serving

Do This

1. Slice the onions, mince the garlic, and grate the Gruyère.
2. Heat the butter and oil in a large Dutch oven. Add the onions and salt; cook for 10 minutes over medium heat, then 50 minutes over medium-low heat, stirring regularly, until deeply golden.
3. Stir in the garlic for 1 minute. Add the wine and scrape up the browned bits; cook for 4 minutes.
4. Add the broth, thyme sprigs, bay leaf, and pepper. Bring to a gentle simmer over 5 minutes, then simmer uncovered for 25 minutes. Remove the thyme stems and bay leaf.
5. Meanwhile, toast the baguette at 425°F (220°C) for 8 minutes, turning halfway through.
6. Divide the soup among 6 broiler-safe crocks. Add 2 toasts and 30 g Gruyère to each. Broil on high for about 3 minutes until bubbling and golden; cool for 5 minutes before serving.

Why You’ll Love This Recipe

Deep flavor from everyday ingredients: Patiently cooked onions provide natural sweetness without added sugar.
A festive, comforting starter: Rich broth and bubbling Gruyère make a lovely beginning to Christmas dinner.
Easy to prepare ahead: Make the soup in advance, then toast, top, and broil just before serving.
A classic cheese-topped finish: Each spoonful brings together silky onions, savory broth, and crisp-edged baguette.

Grocery List

Produce: 1.2 kg yellow onions, 1 head garlic, and 1 small bunch fresh thyme.
Dairy: Unsalted butter and 180 g Gruyère cheese.
Pantry: Olive oil, dry white wine, 1.44 liters low-sodium beef broth, dried bay leaf, fine sea salt, ground black pepper, and 1 small baguette.

Full Ingredients

For the Onion Soup

2 pounds 10 ounces (1.2 kg) yellow onions, weighed before peeling, about 6 large onions
3 tablespoons (42 g) unsalted butter
1 tablespoon (15 ml) olive oil
1/2 teaspoon (3 g) fine sea salt
2 garlic cloves, about 6 g, finely minced
1/2 cup (120 ml) dry white wine, such as Sauvignon Blanc or unoaked Chardonnay
6 cups (1.44 liters) low-sodium beef broth
4 fresh thyme sprigs
1 dried bay leaf
1/4 teaspoon freshly ground black pepper
2 tablespoons (30 ml) water at a time, only if needed to loosen browned bits during caramelization

For the Gruyère Toasts

12 baguette slices, cut 1/2 inch (1.25 cm) thick, about 180 g total
6.3 ounces (180 g) Gruyère cheese, freshly grated
1 teaspoon fresh thyme leaves, optional, for garnish

Step-by-Step Instructions

Step 1: Prepare the onions and toppings

Peel the onions, halve them through the root, and slice them from root to tip into strips about 1/8 inch (3 mm) thick. Even slices cook more consistently and keep a lovely, silky texture in the finished soup. Mince the garlic, grate the Gruyère, and slice the baguette.

Set out a wide, heavy 5- to 6-quart Dutch oven and 6 broiler-safe soup crocks with a capacity of approximately 16 ounces (475 ml) each. Check that the crocks are specifically rated for broiler use; oven-safe does not always mean broiler-safe.

Step 2: Slowly caramelize the onions

Melt the butter with the olive oil in the Dutch oven over medium heat. Add the onions and salt, tossing thoroughly to coat. Cook for 10 minutes, stirring every 2 minutes, until the onions begin to soften and collapse.

Reduce the heat to medium-low and cook for another 50 minutes, stirring every 3 to 5 minutes and more frequently toward the end. Scrape the bottom of the pot as you stir. The onions should become very soft and deep golden brown, with a sweet, savory aroma.

If the bottom develops dark brown patches before the onions are ready, add 2 tablespoons (30 ml) water and scrape them up. Lower the heat if anything starts to blacken. Plan on 60 minutes for this stage, but allow extra time if the onions are still pale; their color matters more than the clock.

Step 3: Add the garlic and deglaze with wine

Stir in the garlic and cook for 1 minute. Pour in the white wine, then scrape the bottom of the pot with a wooden spoon to release the flavorful browned bits. Cook for 4 minutes, stirring occasionally, until the wine has reduced substantially and its sharp aroma has softened.

Step 4: Simmer the soup

Add the beef broth, thyme sprigs, bay leaf, and black pepper. Increase the heat to medium-high and bring to a gentle simmer, allowing approximately 5 minutes. Reduce the heat to low and simmer uncovered for 25 minutes, stirring occasionally. Keep the bubbles gentle rather than letting the soup boil vigorously.

Remove and discard the thyme stems and bay leaf. Keep the soup hot while you finish the toasts. Remember that the Gruyère will add saltiness to each serving.

Step 5: Toast the baguette

During the final 15 minutes of simmering, preheat the oven to 425°F (220°C). Arrange the baguette slices in a single layer on a metal baking sheet. Bake for 8 minutes, turning after 4 minutes, until lightly golden and crisp on both sides.

Remove the toasts. Set an oven rack so the tops of the filled crocks will sit approximately 6 inches (15 cm) below the broiler element. Switch the broiler to high, approximately 500°F (260°C) if your oven offers a temperature setting.

Step 6: Add the Gruyère and broil

Place the broiler-safe crocks on a sturdy, rimmed metal baking sheet without parchment paper. Divide the hot soup evenly among them, leaving at least 3/4 inch (2 cm) of space below each rim. Add 2 baguette toasts to each bowl, overlapping them slightly if needed, and cover each portion with 30 g grated Gruyère.

Broil for approximately 3 minutes, until the cheese is melted, bubbling, and mottled with golden-brown spots. Start checking after 1 minute and continue checking every 30 seconds; remove the crocks sooner if the cheese browns quickly. Never leave the broiler unattended.

Carefully remove the tray using oven mitts. Let the soup stand for 5 minutes, then add the optional thyme leaves. Serve each crock on a heatproof plate and warn everyone that the bowls and soup are very hot.

Pro Tips

Give the onions room: A wide pot helps moisture evaporate. A narrow saucepan makes caramelization slower and less even.
Look for deep gold, not burnt edges: Properly caramelized onions are sweet and richly colored. Blackened onions will make the broth bitter.
Choose the broth carefully: A flavorful low-sodium beef broth gives you depth without making the cheese-topped soup overly salty.
Grate the cheese yourself: Freshly grated Gruyère melts more smoothly than cheese coated with anti-caking ingredients.
No broiler-safe crocks? Divide the Gruyère over the toasted baguette on a metal baking sheet and broil for about 3 minutes. Float the finished cheese toasts on the soup in heat-safe serving bowls.

Variations

Without wine: Replace the white wine with 1/2 cup (120 ml) additional beef broth. Stir in 1 teaspoon (5 ml) sherry vinegar after simmering for a little balancing acidity.
Vegetarian version: Replace the beef broth with the same quantity of rich vegetable or mushroom broth, and use a vegetarian-rennet Alpine-style cheese instead of traditional Gruyère.
A slightly sharper topping: Replace 60 g of the Gruyère with 60 g aged Comté, keeping the total cheese quantity at 180 g.

Storage & Make-Ahead

The soup base is excellent made 1 day ahead, making it especially useful for Christmas entertaining. Transfer it to shallow containers, cool promptly, and refrigerate within 2 hours of cooking. Store without the bread or cheese for up to 4 days in the refrigerator, or freeze for up to 3 months.

Thaw frozen soup overnight in the refrigerator. Reheat in a saucepan over medium heat, stirring occasionally, until it reaches at least 165°F (74°C). Prepare the toasts, assemble the bowls, and broil just before serving. You can also toast the baguette up to 1 day ahead; let it cool completely before storing in an airtight container at room temperature.

Nutrition (per serving)

Estimated for one-sixth of the soup with 2 baguette slices and 30 g Gruyère. Actual values, especially sodium, vary with the broth, bread, and cheese used.