Authentic French Onion Soup (Soupe à l’Oignon Gratinée) 🇫🇷
A highly authentic French Onion Soup (Soupe à l’Oignon Gratinée) recipe, prepared the same way it has been made in Parisian bistros for over a century.
Equipment
- Heavy-bottomed pot or Dutch Oven
- Wooden spatula
- Chef Knife
- Wooden Cutting Board
- French Onion Soup Bowls
- Baking Tray
- Parchment paper
- Box Grater
- Ladle
- Broiler or Oven with grill function
Ingredients
For the onion soup
- 4 –5 large yellow onions about 1 kg, thinly sliced
- 3 tbsp unsalted butter
- 1 –2 tbsp Extra Virgin Olive Oil
- 2 cloves garlic minced
- 1 tbsp flour optional but traditional for thickening
- 150 ml ⅔ cup dry white wine OR dry French vermouth
- 1 liter 4 cups high-quality beef stock (traditional)
- 1 bay leaf
- 2 –3 thyme sprigs
- Salt and black pepper to taste
For the gratinéed topping
- ½ French baguette sliced into thick rounds
- 200 g 2 cups grated Gruyère (traditional) - Comté or Emmental also work
- Optional: a touch of Parmesan for extra browning
Instructions
Step 1 - Caramelize the onions (the most important step!)
- Heat butter and olive oil in a heavy pot (like a Dutch oven).3 tbsp unsalted butter, 1 –2 tbsp Extra Virgin Olive Oil
- Add the sliced onions and a pinch of salt.4 –5 large yellow onions, Salt and black pepper
- Cook on medium-low for 45 minutes to 1 hour, stirring every 15-20 minutes.
- Onions should become a deep golden brown color and will be very soft and jammy.
Step 2 - Build the soup
- Once onions are caramelized, add garlic and cook 1 minute.2 cloves garlic
- Stir in the flour and cook another minute (optional step to slightly thicken).1 tbsp flour
- Deglaze with the white wine, scraping up all browned bits.150 ml ⅔ cup dry white wine OR dry French vermouth
- Add the beef stock, bay leaf, thyme, salt, and pepper.1 bay leaf, 2 –3 thyme sprigs, 1 liter 4 cups high-quality beef stock (traditional)
- Simmer uncovered for 20–25 minutes.
- Taste and adjust seasoning.
Step 3 - Prepare the toasted bread
- Toast baguette slices in the oven until crisp (2-3 minutes under the grill/broiler).½ French baguette
Step 4 - Assemble and broil
- Ladle hot soup into oven-safe bowls.
- Float 2–3 toasted baguette slices on top.
- Cover generously with Gruyère.200 g 2 cups grated Gruyère (traditional) - Comté or Emmental also work, Optional: a touch of Parmesan for extra browning
- Place bowls under a hot broiler for 2-3 minutes until the cheese melts and starts to bubble and become golden. A little browning around the edges is also good for flavor!
Serve
- Serve piping hot — the cheese crust should be gooey, melty, and slightly crisp in spots.
Notes
Tips for TRUE French Flavor
- Use yellow onions, not sweet onions.
- Avoid shortcuts — authentic soup depends on slow caramelization.
- Beef stock is traditional, though half-and-half (Beef/chicken) stock adds balance.
- Gruyère is essential, giving the classic nutty, stringy melt.
- Use dry wine only — sweet wine will throw the flavor off.