Summary: This classic French Onion Soup Gratinée features deeply caramelized onions simmered in a rich beef broth, topped with toasted baguette slices and a bubbling, golden crust of Gruyère cheese. A quintessential bistro staple requiring patience and high-quality ingredients, prepared in 120 minutes for 6 servings.
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Category: Soups, French Cuisine
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Quick overview
- Dish: French Onion Soup Gratinée
- Category: Soups, French Cuisine
- Cuisine: French
- Main ingredient: Yellow onions, 3 lb
- Guide: 12 Most Popular French Dishes: Favorite Recipes of French Cuisine
- Total time: 120 minutes (30 min prep + 90 min cooking)
- Difficulty: Intermediate
- Servings: 6 (Serving weight: 16 oz g)
- Key technique: Caramelization
- Preparation types: Stovetop, Oven-baking
- Dietary info & Allergens: Contains gluten, milk
- Suitable for: Lunch, Dinner
- Nutritional values (per 1 serving): 340 kcal, Protein: 12 g, Fat: 18 g, Carbs: 32 g
- Storage: 3 days in the fridge, 3 months in the freezer
- Pairing: Lager, Pinot Noir, Sparkling Water
- In a nutshell: The ultimate comfort soup with a rich, savory broth and perfectly melted cheese.
- Last updated: September 21, 2026
WAGUU says: “The secret to this soup lies in the slow caramelization of onions, which transforms them into a sweet, deep-brown base.”
Key facts
| Prep time: | 30 min |
| Cooking time: | 90 min |
| Temperature: | 400 °F |
| Number of servings: | 6 |
In a nutshell
This soup is a masterpiece of simple ingredients. Slow-cooked onions create a complex flavor profile that pairs beautifully with the nutty, melted Gruyère crust.
Ingredients
Base servings: 6 servings • Serving weight: 16 oz g
| Ingredient | Quantity | Quality |
|---|---|---|
| Yellow onions | 3 lb | Thinly sliced |
| Unsalted butter | 4 tbsp | High-fat |
| Beef stock | 6 cups | Rich and homemade |
| Gruyère cheese | 12 oz | Aged |
| Baguette | 6 slices | Day-old |
| Salt | 2 tsp | Kosher |
Why you’ll love this recipe
- Depth of Flavor: The slow caramelization process creates a sweet, savory umami base that defines authentic French onion soup.
- Textural Harmony: The contrast between the soft, melt-in-your-mouth onions and the crisp, toasted baguette is unparalleled.
- Gratinée Finish: The bubbling, golden-brown crust of aged Gruyère provides a nutty, satisfying finish to every bowl.
Success guaranteed: By following the temperature guidelines and allowing the onions to darken slowly, you ensure a deep, professional-grade result.
Recipe overview
Prep: 30 min | Cooking: 90 min | Difficulty: Intermediate | Servings: 6 | Type: Soup | Origin: France
Detailed instructions
Overall progress: 0% completed
Phase 1: Onion Caramelization – 60 min
Appliances: Stove
1. Melt 4 tbsp butter in a large heavy-bottomed pot. Add 3 lb sliced yellow onions and 1 tsp salt. Cook over medium-low heat, stirring occasionally, until the onions are deep golden brown and reduced in volume.
CP: Visual check point (VKB): Onions should have a dark, syrupy consistency without burning.
Phase 2: Soup Simmering – 20 min
Appliances: Stove
2. Pour 6 cups of beef stock into the pot with the caramelized onions. Bring to a gentle simmer and cook for 20 minutes to meld the flavors. Season with the remaining 1 tsp salt.
CP: VKB: The soup should have a clear, dark broth with tender, soft onions.
Phase 3: Gratinée Finish – 10 min
Appliances: Oven
3. Preheat oven to 400 °F. Ladle soup into oven-safe bowls. Top each with a baguette slice and a generous amount of grated Gruyère. Bake for 10 minutes until the cheese is melted and golden brown.
CP: VKB: The cheese must be bubbling and have a dark golden crust.
Required equipment
| Utensil | Ideal size | Alternative | Risk |
|---|---|---|---|
| Heavy-bottomed pot | 6-quart | Dutch oven | Burning onions |
| Oven-safe bowls | 12-oz capacity | Ramekins | Bowl breakage |
| Chef’s knife | 8-inch | Mandoline | Uneven slices |
Shopping list
Nutrition profile
Values per 1 serving (excluding side dishes). Calculated from average ingredient nutrition values.
| Nutrient | Per 3.5 oz (100 g) | Per 1 serving | Total |
|---|---|---|---|
| Energy | 75.5 kcal | 340.0 kcal | 2040.0 kcal |
| Fat | 4.0 g | 18.0 g | 108.0 g |
| of which saturates | 2.5 g | 11.2 g | 67.2 g |
| Carbohydrates | 7.1 g | 32.0 g | 192.0 g |
| of which sugars | 3.3 g | 14.8 g | 88.8 g |
| Protein | 2.7 g | 12.0 g | 72.0 g |
| Salt | 0.25 g | 1.1 g | 6.6 g |
Reference intake of an average adult (8400 kJ / 2000 kcal).
WAGUU Pro level
- Pro standard: Verified recipe with precise ratios and visual checkpoints.
- Tip 1: Use a mix of onion varieties (yellow and red) for a more complex flavor profile.
- Tip 2: Deglaze the pot with a splash of dry white wine or cognac before adding the stock.
- Tip 3: Ensure the baguette slices are toasted until firm to prevent them from turning mushy.
- Tip 4: Use a blend of Gruyère and Comté for a more nuanced nutty flavor.
Scientific background
The Maillard reaction, triggered by the slow heating of onions, breaks down their complex sugars and amino acids. This creates the characteristic deep-brown color and sweet, savory flavor profile necessary for a high-quality soup.
Fine Dining – Professional techniques
- Plate composition: Use elegant, dark-rimmed oven-safe crocks for a professional look.
- Texture contrasts: Ensure the baguette is crunchy enough to withstand the hot broth for several minutes.
- Temperature contrast: Serve immediately while the surface is bubbling hot, but ensure the center is manageable.
- Aromatic garnishes: Top with fresh, finely chopped chives before serving for a vibrant color contrast.
Sensory radar
- Appearance: Deep golden brown broth with a thick, melted cheese cap.
- Aroma: Rich, caramelized onion scent with subtle roasted nut notes.
- Taste: Sweetness of onions balanced by the savory, salty depth of beef stock and aged cheese.
- Texture: Silky broth, tender onions, and a crisp bread-and-cheese crust.
Pairing
- BEER: A crisp, light-bodied Lager to cut through the richness of the Gruyère.
- WINE: A light-bodied Pinot Noir or an unoaked Chardonnay.
- NON-ALCOHOLIC: Sparkling mineral water with a twist of lemon.
Various preparation methods
- Slow Cooker Version: Caramelize onions on the stove first, then transfer to a slow cooker with beef stock and simmer on low for 6 hours.
- Vegetarian Version: Substitute high-quality vegetable stock and a splash of soy sauce for the beef broth to maintain depth.
Allergens and dietary information
Contains: Gluten, Milk • Gluten: Contains wheat in the baguette • Not suitable for: Vegan, Lactose-free diets
Suitable for
Comfort food enthusiasts, dinner parties, and those looking for a traditional French bistro experience.
Substitution guide
- Gruyère: Emmental or Fontina for a different melt.
- Beef stock: A high-quality chicken or vegetable stock for a lighter soup.
FAQ
Can I use red onions?
Yes, but they may result in a slightly sweeter soup and a darker, more purple-hued broth.
How do I prevent the bread from getting mushy?
Toast the baguette slices until they are quite hard before adding them to the soup.
Can I make this ahead of time?
Yes, the soup base improves with time, but add the bread and cheese just before baking.
Why did my onions burn?
The heat was likely too high. Caramelization requires low heat and patience to avoid bitterness.
WAGUU Petr advises: Cooking for 12 or more people?
12–16 people: Use two large pots to caramelize the onions simultaneously to ensure even cooking. 20+ people: Prepare the soup base a day in advance; the flavors will deepen, and you can focus on the gratinée step during the event.
Sides and serving
- Mixed Green Salad – With a light vinaigrette to balance the richness.
- Crusty Bread – For dipping into the broth (not included in the recipe).
Serving: Serve steaming hot in individual oven-safe bowls, ensuring the cheese crust is intact.
Storage and reheating
Fridge: 3 days • Freezer: 3 months • Reheating: Gently simmer on the stove; add bread and cheese just before serving.
Author: WAGUU Petr & Team • Published: 21 Sep 2026 • Updated: 30 Oct 2026
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Common mistakes
- Insufficient Caramelization: Skipping the 60-minute onion cook leads to a bland, pale soup.
- Overloading the Bowl: Adding too much bread prevents the cheese from forming a proper seal.
- Using Low-Quality Stock: The soup relies entirely on the quality of the beef stock for flavor.
- Improper Oven Temperature: Not using a high enough temperature prevents the cheese from browning correctly.