Classic French Onion Soup
This classic French Onion Soup recipe delivers rich, deep flavor through slow caramelization of onions, a savory broth, and a gratinated cheesy baguette topping, making it the ultimate comforting meal.
For 6 servings
Prepare Onions: Halve the yellow onions, then thinly slice them using a sharp knife or mandoline. Aim for uniform slices, about 1/8-inch thick. This ensures even caramelization. Grate the Gruyère cheese and slice the baguette into 1-inch thick rounds.
Caramelize Onions: In a large, heavy-bottomed pot or Dutch oven, melt the butter and olive oil over medium-low heat. Add the sliced onions and a pinch of salt. Cook slowly, stirring occasionally (every 5-10 minutes), for 45-60 minutes, or until the onions are deeply golden brown, very soft, and significantly reduced in volume. Be patient; this step is crucial for flavor. If they start to stick, add a tablespoon of water.
Build Flavor Base: Sprinkle the all-purpose flour (if using) over the caramelized onions and stir for 1-2 minutes to cook out the raw flour taste. Pour in the dry sherry or white wine, scraping the bottom of the pot with a wooden spoon to deglaze and release all the flavorful browned bits. Let it simmer for 2-3 minutes until the liquid has mostly evaporated.
Simmer the Soup: Add the beef broth, fresh thyme sprigs, and bay leaf to the pot. Bring the soup to a gentle simmer, then reduce the heat to low, cover partially, and let it cook for at least 30 minutes (or up to 2 hours for deeper flavor).
Season and Prepare Toasts: Remove the thyme sprigs and bay leaf. Season the soup with salt and freshly ground black pepper to taste. While the soup simmers, preheat your oven broiler. Arrange the baguette slices on a baking sheet and toast them lightly under the broiler until golden brown, about 1-2 minutes per side.
Assemble and Gratiné: Ladle the hot soup into oven-safe bowls. Float 1-2 toasted baguette slices on top of each bowl. Generously sprinkle the grated Gruyère cheese (and optional Parmesan) over the baguette, ensuring it covers the bread and slightly spills into the soup.
Broil to Perfection: Place the soup bowls on a baking sheet (to catch any drips) and carefully transfer them to the preheated broiler. Broil for 2-4 minutes, watching constantly, until the cheese is melted, bubbly, and golden brown.
Serve Immediately: Carefully remove the hot bowls from the oven using oven mitts. Let them cool for a minute or two before serving. Enjoy the classic French Onion Soup piping hot!
What to keep in mind.
4 tips from the recipe — small details that make a real difference to the final dish.
- 1Patience is Key: Do not rush the caramelization of the onions. This slow process develops the deep, sweet, and savory foundation of the soup. Low and slow is the way to go.
- 2Quality Broth: Use a high-quality beef broth or homemade stock. It makes a significant difference in the final flavor profile. Avoid overly salty or artificial-tasting broths.
- 3Freshly Grated Cheese: Always grate your own Gruyère. Pre-shredded cheeses often contain anti-caking agents that can affect melting and flavor.
- 4Oven-Safe Bowls: Ensure your soup bowls are genuinely oven-safe and can withstand high broiler temperatures to prevent cracking.
Adapt it for your goals.
Vegetarian/Vegan
Replace beef broth with good quality vegetable broth, use vegan butter, and opt for a plant-based, meltable cheese alternative for a delicious meat-free version.
Mushroom Umami BoostMushroom Umami Boost
Add 1 cup of thinly sliced cremini mushrooms along with the onions during caramelization for an extra layer of earthy umami flavor.
Slow Cooker MethodSlow Cooker Method
After caramelizing the onions on the stovetop, transfer them to a slow cooker with the broth, wine, and herbs. Cook on low for 4-6 hours for an even deeper flavor development. Finish with cheese toasts under the broiler.
Why this is on our healthy list.
Rich in Antioxidants
Onions are packed with antioxidants like quercetin, which can help reduce inflammation and protect cells from damage.
Gut-Friendly Prebiotics
Slowly cooked onions contain prebiotics, which feed beneficial gut bacteria, supporting digestive health.
Comforting and Satisfying
While not a 'diet' food, the warmth, richness, and satisfying nature of this soup can contribute to mental well-being and a sense of comfort.
Frequently asked questions
Yes, French Onion Soup actually tastes better the next day! Prepare the soup up to step 5 (before adding cheese toasts) and refrigerate. Reheat gently on the stovetop, then proceed with the cheese toast and broiling steps just before serving.
