French onion soup: the timeless classic that never goes out of style

A warm bowl of French onion soup is comfort in a spoon: sweet, savory, and topped with bubbling cheese. This easy recipe turns everyday onions and a stale baguette into a satisfying, gratinéed classic. Read on for clear steps, timing, and tips to get perfect caramelization and a golden crust every time.

Ingredients for French onion soup (serves 6)

• 500 g onions, peeled
• 60 g unsalted butter
• 1 tbsp all-purpose flour
• 1 bouillon cube (vegetable or beef)
• 1 tbsp granulated sugar
• 2 L water
• Fresh or dried thyme, to taste
• Salt and black pepper
• 1 stale baguette, sliced
• 200 g grated cheese (Gruyère or Emmental recommended)

Essential cookware and small extras

• Large heavy-bottomed pot or Dutch oven
• Sharp knife and cutting board
• Wooden spoon or heatproof spatula
• Ovenproof bowls or ramekins for gratinating
• Baking tray for toasting bread

How to make caramelized onion soup — step by step

1. Prepare and soften the onions

1. Thinly slice the onions. Keep slices even for uniform cooking.
2. Melt the butter in the pot over medium heat.
3. Add the onions and cook, stirring often. Stir regularly to avoid burning.
4. If the onions begin to stick, splash a little water and continue cooking.

2. Caramelize until deeply golden

1. Sprinkle sugar over the onions to encourage browning.
2. Continue cooking until the onions reach a deep amber color.
3. This stage takes time but builds the soup’s signature flavor.

3. Build the broth and simmer

1. Lightly dust the onions with flour and stir to coat.
2. Add the water, bouillon cube, thyme, salt, and pepper.
3. Bring to a gentle boil, then reduce heat to medium-low and cover.
4. Simmer for about 45 minutes to blend flavors.

4. Assemble and gratinate

1. Ladle the soup into ovenproof bowls.
2. Top with toasted baguette slices, then a generous layer of grated cheese.
3. Place bowls under a hot grill for about 10 minutes or until the cheese bubbles and browns.
4. Watch closely under the grill to avoid burning the cheese.

Quick tips and variations for better results

• Add one bay leaf or 100 ml dry white wine to the broth for extra aroma.
• Use a mix of butter and olive oil to reduce saturated fat while keeping flavor.
• Swap the bouillon cube for 2 L homemade or low-sodium stock for richer depth.
• For a vegetarian version, choose vegetable bouillon and a vegetarian cheese.
• Toast baguette slices before topping to keep them from going soggy too fast.

Nutritional information (per serving, approx.)

• Calories: 377 kcal
• Carbohydrates: 34.3 g
• Fat: 19.4 g
• Saturated fat: 12.4 g
• Protein: 14.6 g
• Fiber: 2.7 g
• Sugars: 8.1 g

Wine pairings that complement onion soup

• Alsace Pinot Noir — light red, good with cheesy gratin
• Bourgogne Aligoté — crisp white to cut richness
• Alsace Sylvaner — fresh white, pairs well with caramelized flavors

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Harper James

Harper is a recipe developer with a deep love for seasonal produce and rustic simplicity. She brings a farm-to-table philosophy to life with every dish she creates, celebrating the beauty of fresh, accessible ingredients.