Classic French Onion Soup

Rich, caramelized onions simmered in a flavorful, savory broth and topped with golden, bubbly cheese—French Onion Soup is the definition of cozy comfort. This beloved French dish may look fancy, but it’s actually simple to make once you know the right steps. In this guide, I’ll walk you through every detail, from perfectly caramelizing the onions to broiling the cheesy topping until it’s beautifully golden.

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A Timeless Classic with Humble Origins

While French Onion Soup has earned its place on fine-dining menus around the world, its beginnings are humble. Originally a peasant dish made from onions, stale bread, and water, it has evolved into something truly elegant. The magic lies in transforming basic ingredients through time and technique—slow-cooked onions, a touch of wine, and a hearty broth combine to create something deeply satisfying and full of character.

The secret ingredient? Patience. The onions need to cook low and slow until they turn a rich, golden brown. Their natural sugars caramelize, developing a deep sweetness that forms the foundation of the soup’s irresistible flavor. Once that’s done, everything else comes together easily.

What You’ll Need to Make French Onion Soup

Butter and Olive Oil: The perfect duo for caramelizing onions—the oil prevents the butter from burning, giving you control over the process.
Sweet Onions (such as Vidalia): These develop the best flavor when caramelized—soft, sweet, and perfectly balanced.
Sugar: Just a pinch helps speed up the caramelization process and intensify the onion’s natural sweetness.
Dry White Wine: Used to deglaze the pan, lifting up all those browned bits and adding depth to the broth.
All-Purpose Flour: Helps the soup thicken slightly for a velvety texture.
Beef Broth, Worcestershire Sauce, Dried Thyme, and Bay Leaves: Together, they create a savory base rich in umami.
Baguette: Crisped and layered with cheese to make the classic topping.
Dry Sherry: Adds complexity and a slightly nutty sweetness to finish the soup.
Gruyère and Parmigiano Reggiano: The signature cheeses—creamy, nutty, and wonderfully melty. Always opt for high-quality imported cheeses if possible for the best flavor.

Step-by-Step Instructions

Step 1: Caramelize the Onions

Start by melting the butter in a large, heavy pot or Dutch oven over medium heat. Add the olive oil, sliced onions, salt, pepper, and sugar. Stir occasionally, cooking slowly until the onions turn a deep golden brown and become completely soft and caramelized—this will take about 50 minutes. The goal is rich color and sweetness, not burnt edges, so keep the heat moderate and be patient. Your kitchen will smell incredible.

Step 2: Deglaze the Pan

Pour in the white wine to deglaze, using a wooden spoon to scrape up any browned bits stuck to the bottom of the pan. These bits, known as “fond,” are flavor gold. Continue to cook until the wine has mostly evaporated and the onions look jammy and glossy.

Step 3: Thicken the Base

Sprinkle the flour over the onions and stir for about a minute, just until it disappears. This step helps create a slightly thicker and heartier broth later on.

Step 4: Build the Broth

Add the beef broth, Worcestershire sauce, thyme, and bay leaves. Bring everything to a gentle boil, then reduce the heat to low and let it simmer for about 30 minutes. The flavors will meld beautifully, creating a deep, rich soup base. When it’s done, stir in the sherry for a final layer of complexity.

Step 5: Toast the Bread

While the soup simmers, preheat your oven to 400°F (200°C). Arrange the baguette slices on a baking sheet in a single layer and toast until golden and crisp, about 10 minutes. Set aside to cool.

Step 6: Assemble the Crocks

When you’re ready to serve, set your oven broiler to high. Place oven-safe soup crocks on a baking tray for easy handling. Ladle hot soup into each crock, top with a toasted baguette slice, and cover generously with the grated cheeses.

Step 7: Broil and Serve

Slide the crocks under the broiler until the cheese is melted, bubbling, and lightly golden—usually 2 to 4 minutes. Be careful when removing them, as the crocks will be very hot. Let them cool for a few minutes before serving.

The result? A bowl of French Onion Soup that’s rich, savory, and topped with the ultimate cheesy crust—a perfect balance of sweetness, saltiness, and umami in every spoonful.

Tips for Success

• Don’t rush the onions: Caramelization takes time. The longer they cook, the deeper and sweeter the flavor.
• Use good cheese: Authentic Gruyère and Parmigiano Reggiano make a huge difference.
• Broil carefully: Keep an eye on the cheese to prevent burning—it melts quickly under high heat.
• Make ahead: The soup itself (without the bread or cheese) keeps well for up to three days in the fridge or three months in the freezer. Just reheat and assemble before serving.

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