Hi! I’m Cassandre, and today on Caramel Loafing, we’re warming up with a pot of authentic French onion soup—La Soupe à l'oignon gratinée. Ready to chase away the chill and fill your kitchen with cozy, savory aromas?
When it comes to French soups, nothing is more iconic than onion soup. Its signature flavor comes from deeply caramelized onions, slowly cooked over low heat until golden and jammy, then simmered in a rich, savory broth. The finishing touch? A slice of garlic-rubbed baguette, topped with melty cheese and baked until golden. Gooey cheese, broth-soaked bread, and tender onions in every bite—pure comfort in a bowl.
While it may sound intimidating, authentic French onion soup is surprisingly simple to make. All it takes is time and patience. The key is to cook the onions low and slow until they develop that deep color and irresistible sweetness.
At the end of this recipe, I’ll share a few tips to help you bring restaurant-level flavor right to your own kitchen. I hope you love it as much as I do!
Craving more delicious ideas? Try these next:
A bold, timeless French favorite: Chicken Cordon Bleu
Warm, creamy, and comforting: Corn Chowder
Deceptively simple yet seriously satisfying: Potato Gratin (French Scalloped Potatoes)
Cool, crisp, and perfect for summer: Spanish Gazpacho
Comforting and rich with French flavor: Creamy French Mushroom Soup
Rich, velvety, and made for cozy fall and winter nights: French Pumpkin Soup
Classic French Onion Soup Recipe
Ingredients
Yields: 2–3 servings
- Onions – 600g (21.2 oz)
- Fresh herbs – a few sprigs (bay leaves and thyme)
- Red wine – 150ml (5 fl oz)
- Sugar – 5g (0.18 oz)
- Black pepper – ½ tsp
- Broth – 500ml (16.9 fl oz)
- Baguette – 2 to 3 slices
- Unsalted butter – 25g (0.88 oz)
- Grated cheese – to taste (Gruyère, cheddar, mozzarella all work well)
- 1 garlic clove (peeled)
Instructions
- Trim off the root and stem ends of the onions, then cut them in half.
- Peel off the outer skin and the first tough layer (which can feel a bit plasticky).
- Place the flat side down and slice the onions following the grain (a classic French cut). This helps the slices hold their shape during long cooking.
- Heat a pot with the butter and a splash of olive oil (or vegetable oil). Add the sliced onions and sauté gently over medium-low heat for about 5 minutes.
- Add the bay leaves and thyme, stir briefly, then cover and reduce to low heat. Let steam for 15 minutes.
- Uncover. The onions should now be soft and translucent. Continue cooking uncovered over low heat, stirring occasionally, until most of the moisture evaporates and the onions turn golden and jammy—about 18–20 minutes.
- Remove the herbs. Deglaze the pot with red wine, scraping up any browned bits from the bottom, and simmer for 15 minutes.
- Pour in the broth. If the broth is already salted, skip the salt—just season with black pepper. Once it comes to a boil, reduce heat and simmer for 10–12 minutes.
- While the soup simmers, toast the baguette slices in a preheated oven at 430°F (220°C) for 8 minutes until golden. Rub the toasted slices with raw garlic.
- Ladle the soup into oven-safe bowls, place a garlic toast on top, then sprinkle generously with grated cheese. Broil at 430°F (220°C) for about 11 minutes, or until the cheese is melted and bubbly with golden edges. Serve hot.
Watch the full step-by-step video here: How to Make Classic French Onion Soup