If you're craving a bowl of pure comfort, this French Onion Soup is absolutely dreamy! Imagine deeply caramelized onions swimming in a savory, aromatic broth, crowned with a golden, gooey layer of melted Gruyère atop a slice of toasted baguette. This classic bistro staple is hearty, luxurious, and just bursting with rich, umami flavors that linger long after the last spoonful.

What makes this recipe a must-try? It's surprisingly easy, perfect for impressing guests or treating yourself on a cozy night in. You only need a handful of basic ingredients to create a soup that tastes like it came from your favorite French restaurant.

This is my go-to dish anytime I want to turn an ordinary dinner into something special. Whether you serve it as a decadent starter at your next dinner party or as a soul-warming main for family night, this is French comfort food at its best!

Classic French Onion Soup brimming with caramelized onions and cheesy bread

Why You'll Love This Recipe

Bold, deep flavors from perfectly caramelized onions and rich broth
Crowd-pleasing and elegant, yet easy enough for a weeknight
Cheesy, toasty baguette topping that makes every bite irresistible
Budget-friendly with just a few simple pantry staples

Key Ingredients for French Onion Soup

See recipe card below for full list of measurements, ingredients, and instructions.

Yellow Onions

The star of the show, yellow onions lend the soup its signature sweet and savory depth. Take your time slicing them evenly for uniform cooking. For best results, avoid sweet varieties-plain yellow onions develop the richest, most balanced flavor as they caramelize. If you only have white or red onions, they'll work in a pinch, though red will give a more intense flavor and color.

Beef Broth

A hearty, robust beef broth forms the foundation of classic French Onion Soup. Opt for a high-quality, low-sodium broth or homemade if you have it. If you prefer a lighter version, you can use chicken or vegetable broth-just know you'll sacrifice some of that deep, meaty flavor.

Gruyère Cheese

Gruyère is the classic choice for French Onion Soup, prized for its nutty flavor and excellent melting qualities. If needed, try Emmental or Swiss cheese for a similar savory note. For a more budget-friendly option, mozzarella or even sharp white cheddar will do, though the flavor will be different.

Baguette

Thick slices of day-old baguette soak up the broth beautifully while holding their texture under the broiler. No baguette? Any rustic, crusty bread will work-just be sure to toast it before adding to the soup. Gluten-free baguette is a great option for those avoiding gluten.

Fresh Thyme

A sprig of fresh thyme adds an herby, aromatic note that brightens the soup. No fresh thyme? Use a small amount of dried thyme or even an herbes de Provence blend, but keep it light to avoid overpowering the onions.

Instructions for French Onion Soup

See recipe card below for full list of measurements, ingredients, and instructions.

Caramelize the Onions

Start by heating the butter and olive oil in a large Dutch oven or heavy-bottomed pot over medium-low heat. Add the sliced onions and sprinkle with sugar. Cook, stirring frequently, for 30-40 minutes. The onions should become very soft, deep golden brown, and caramelized. Be patient-this step builds the soup's rich base!

Add Garlic and Flour

Stir in the minced garlic and cook for 1 minute until fragrant. Sprinkle over the flour and continue stirring for another 2-3 minutes. This will help thicken the soup a little and give it a silky body.

Deglaze and Simmer

Pour in the white wine (if using), scraping up any browned bits from the bottom of the pot. Let it simmer for 2-3 minutes to reduce slightly. Add the beef broth, bay leaf, and thyme. Bring to a gentle simmer and cook, uncovered, for another 20 minutes. Season with salt and black pepper to taste. Remove the bay leaf and thyme stems before serving.

Toast the Baguette

While the soup simmers, preheat your oven to 400°F (200°C). Arrange the baguette slices on a baking sheet and toast for 5-7 minutes, flipping once, until golden and crisp. Set aside.

Assemble and Broil

Ladle the hot soup into oven-safe bowls or crocks. Top each bowl with a slice or two of baguette, then generously sprinkle with Gruyère (and Parmesan, if using). Place the bowls on a baking sheet and broil on high for 2-3 minutes, or until the cheese is melted, bubbling, and golden brown.

Serve and Enjoy

Carefully remove the bowls from the oven (they'll be hot!). Let them cool slightly, then serve immediately, savoring every cheesy, savory spoonful.

Recipe Variations

Vegetarian French Onion Soup

Swap the beef broth for a good-quality vegetable broth to keep things vegetarian without sacrificing depth of flavor. Add a splash of soy sauce or a dash of miso paste for extra umami!

Make It Gluten-Free

Use your favorite gluten-free baguette or bread for the crouton topping, and substitute the all-purpose flour with a gluten-free flour blend or even cornstarch.

Flavor Boost: Add a Splash of Sherry

For an elegant touch, stir in a tablespoon or two of dry sherry or brandy at the end of cooking. It adds subtle complexity and a classic French flavor.

Extra Cheesy

If you're a cheese lover, mix Gruyère with a little sharp white cheddar or fontina for an even gooier, more decadent finish.

Herbs and Aromatics

Experiment with fresh rosemary or a pinch of herbes de Provence in place of or alongside thyme for a different aromatic profile.

Serving Suggestions

French Onion Soup shines as a starter but easily stands alone as a cozy meal. Pair it with a simple green salad dressed in vinaigrette or a platter of roasted root vegetables for a hearty French-inspired dinner. For garnish, add a grind of black pepper, a sprinkle of fresh thyme, and maybe an extra shaving of Gruyère right before serving.

Storage and Reheating

Leftover soup (without the bread and cheese topping) keeps well in the fridge for up to 4 days. Store in an airtight container. Reheat on the stove over low heat, stirring occasionally until hot. For freezing, cool the soup completely and freeze in airtight containers for up to 2 months. Always add fresh toasted bread and cheese when you're ready to serve for best texture-assemble and broil just before eating!

Frequently Asked Questions About French Onion Soup (FAQ)

Q: Can I make French Onion Soup ahead of time?

A: Yes! The soup base actually improves with time. Prepare the soup (minus bread and cheese) up to 2 days ahead, then reheat and top with fresh baguette and cheese before serving.

Q: What if I don’t have oven-safe soup bowls?

A: No problem! Toast the bread slices with cheese on a baking sheet, then float one on each bowl of hot soup before serving.

Q: Do I have to use Gruyère cheese?

A: Gruyère is the classic, but you can substitute Emmental, Swiss, or even a sharp white cheddar for a different but delicious cheesy crust.

Craving cozy comfort food? This French Onion Soup is classic French bistro fare that's easy to master and guaranteed to impress-rich, cheesy, and deeply satisfying. Give it a try, then leave a comment or rating below to let me know how it turned out!