Classic French Onion Soup with Gruyere and Mozzarella Recipe

If you’re craving something cozy, rich, and downright soul-warming, this Classic French Onion Soup with Gruyere and Mozzarella recipe is exactly what you need. It’s one of those dishes that feels like a warm hug on a chilly day, combining sweet caramelized onions with a deeply savory broth—and then topping it all off with bubbly, golden cheese. I love making this soup when I want to impress guests or just treat myself to something special at home. Plus, it’s deceptively simple to pull off once you know the tricks!

What makes this Classic French Onion Soup with Gruyere and Mozzarella recipe truly stand out is the blend of Gruyere’s nutty richness and the gooey stretchiness of the Mozzarella on top. The combo creates a beautiful cheesy crust that I find irresistible every time. Whether it’s a casual weeknight or a weekend dinner party, this recipe hits the spot perfectly—you’ll want to keep a batch ready to go in your culinary arsenal.

Ingredients You’ll Need

Each ingredient plays its part to bring this soup together: from the sweet onions to the hearty broth and the magic cheeses. I always recommend picking good quality onions and fresh cheese—these small choices make a big difference in taste.

• Unsalted butter: Helps caramelize the onions without adding extra salt, giving you better control over seasoning.
• Yellow onions: Their natural sweetness is perfect for caramelizing, which is key to the flavor depth.
• Salt: Enhances the onions and balances flavors throughout the soup.
• Granulated sugar: A little sugar speeds up the caramelization process—trust me, it’s worth it.
• Garlic: Adds a gentle punch of savory aroma without overpowering.
• Dry red wine: Adds acidity and layers of flavor; pick one you’d enjoy sipping.
• Low-sodium beef broth: Forms the rich, meaty backbone of the soup.
• Low-sodium chicken broth: Lightens the broth slightly, balancing beef’s intensity.
• Worcestershire sauce: A secret umami booster that deepens the broth’s complexity.
• Fresh thyme: Aromatic herb that pairs beautifully with onion and beef flavors.
• Bay leaf: Adds subtle earthiness once simmered, but remember to remove before serving!
• Balsamic vinegar: A splash brightens and rounds out the soup’s flavor.
• French bread slices: The classic soak-and-cheese base—go for a crusty loaf.
• Olive oil: Used to toast the bread to golden perfection before adding cheese.
• Gruyere cheese: Melts into a creamy, flavorful blanket that’s the star on top.
• Mozzarella cheese: Adds that stretchy, gooey texture for cheesier indulgence.
• Parmesan cheese: A sharp finishing touch that cuts through richness with elegance.

Variations

I love playing around with this Classic French Onion Soup with Gruyere and Mozzarella recipe depending on the season or who I’m cooking for. Feel free to make it your own!

• Vegetarian twist: Swap beef broth for mushroom or vegetable broth, and skip Worcestershire sauce or use a vegan version. I once made this for friends and it was just as comforting!
• Spicy kick: Add a pinch of smoked paprika or cayenne for a subtle warm heat. It gives a great surprise without overpowering the signature flavors.
• Herb variations: Try rosemary instead of thyme for a different herbal note; it’s something I started doing last winter and loved the earthiness it added.
• Cheese combos: Swap Mozzarella for Fontina or even Emmental if you want a different melt and taste profile. I’ve found this keeps the soup interesting every time I make it!

How to Make Classic French Onion Soup with Gruyere and Mozzarella Recipe

Step 1: Caramelize Those Onions Slowly and Patiently

This first step really sets the tone. Melt your butter over medium heat, toss in the thinly sliced yellow onions, salt, and sugar. Stir occasionally and mix well to coat the onions. You’ll want to cook them low and slow—about 45 minutes to an hour—until they turn a deep golden brown and smell irresistibly sweet and rich. Don’t rush this; patience here means depth of flavor later. If they’re sticking a bit, add a splash of water or lower the heat.

Step 2: Deglaze and Add Aromatics

Once your onions are beautifully caramelized, pour in the dry red wine to deglaze the pan, scraping up all those tasty browned bits. Let it reduce by half—that concentrates the flavors and mellows the alcohol. Then add minced garlic, Worcestershire sauce, thyme sprigs, bay leaf, and both broths. Bring it to a simmer and cook gently for 30 minutes so all the flavors meld beautifully.

Step 3: Toast the Bread and Prep the Cheese

While the soup simmers, brush your French bread slices with olive oil and toast them in the oven or on a skillet until golden and crisp. This helps them hold up when you ladle soup on top. Mix your Gruyere, Mozzarella, and Parmesan cheeses together so they’re ready to go. Bringing the cheese to room temperature means it melts evenly and beautifully in the oven later.

Step 4: Assemble and Broil to Perfection

Ladle the hot soup into oven-safe bowls, float a toasted bread slice on top, and pile on a generous amount of your cheese blend. Place the bowls on a baking sheet and broil in your oven until the cheese bubbles and turns golden brown, usually 3 to 5 minutes. Keep a close eye so it doesn’t burn—this is your moment of cheesy glory!

How to Serve Classic French Onion Soup with Gruyere and Mozzarella Recipe

Garnishes

I like to keep it simple: a sprinkle of fresh thyme or finely chopped parsley adds a pop of color and a subtle fresh note that cuts the richness. Some days, I toss a few cracked black peppercorns on top for a bit more bite. These little touches make the presentation feel special without overcomplicating the flavors.

Side Dishes

This soup stands wonderfully on its own, but if you’re looking to round out the meal, I often serve it with a crisp green salad with a lemon vinaigrette to brighten things up. A simple roasted vegetable platter or a light charcuterie board also pairs perfectly—great for a cozy dinner with friends or family.

Creative Ways to Present

For a fun twist when hosting, I like to serve the soup in mini French onion soup crocks or even little ramekins, letting each person build their own cheesy crown. You could also sprinkle extra cheese or fresh herbs artistically on top or add a drizzle of truffle oil for an indulgent flair. Presentation makes it feel like an event, even if it’s just a weeknight treat.

Make Ahead and Storage

Storing Leftovers

I usually keep leftover soup without the bread and cheese in an airtight container in the fridge for up to 3 days. This way, the broth stays fresh and you can always toast new bread and grate more cheese when ready to reheat. It saves a lot of last-minute prep time while keeping that fresh oven-baked feeling.

Freezing

I’ve frozen the soup base without issues—just cool it completely, then transfer to freezer-safe containers. When I thaw it later, I make sure to add fresh toasted bread and cheese right before serving. The texture of frozen and thawed caramelized onions does hold up well, so this is a great way to have a ready-made meal that feels homemade.

Reheating

Reheat the soup gently on the stove over medium-low heat, stirring occasionally to prevent scorching. When warmed through, ladle into oven-safe bowls, add fresh toasted bread and cheese, then broil as you would the first time to revive that signature cheesy crust. This method helps keep the taste bright and the textures just right.

FAQs

Final Thoughts

This Classic French Onion Soup with Gruyere and Mozzarella recipe has become one of my go-to comfort foods because it’s both elegant and approachable. The layers of flavor—from the sweet onions to the melty cheese topping—feel like a small culinary celebration every time I make it. I’m confident that once you try this recipe, you’ll find yourself reaching for it whenever you want something satisfying and special. Give it a go—you’ll enjoy the process as much as the delicious results!

Classic French Onion Soup with Gruyere and Mozzarella Recipe

★★★★★ 4.7 from 92 reviews

• Author: Touba
• Prep Time: 15 minutes
• Cook Time: 1 hour 15 minutes
• Total Time: 1 hour 30 minutes
• Yield: 5 servings 1x
• Category: Soup
• Method: Stovetop
• Cuisine: French
• Diet: Low Salt

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Description

A classic French Onion Soup recipe featuring caramelized onions simmered in a rich blend of beef and chicken broths, enhanced with red wine, herbs, and balsamic vinegar. Topped with toasted French bread slices and a gooey blend of Gruyere, Mozzarella, and Parmesan cheeses, this comforting soup is perfect for cozy dinners or entertaining guests.

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Ingredients

Scale 1x2x3x

Sauté Base

• 4 tablespoons unsalted butter
• 5 large yellow onions, thinly sliced
• 1 teaspoon salt
• 1 teaspoon granulated sugar
• 2 cloves garlic, minced

Soup

• 1/2 cup dry red wine
• 32 ounces low-sodium beef broth
• 24 ounces low-sodium chicken broth
• 1 tablespoon Worcestershire sauce
• 2 sprigs fresh thyme
• 1 bay leaf
• 1/2 tablespoon balsamic vinegar
• Pinch of salt and freshly ground black pepper, to taste

Toppings

• 5 1-inch thick slices of French bread
• 2 tablespoons olive oil
• 1 1/2 cups shredded Gruyere Swiss cheese, room temperature
• 1/4 cup shredded Mozzarella cheese, room temperature
• 2 tablespoons finely grated Parmesan cheese, room temperature

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Instructions

1. Caramelize the Onions: In a large heavy-bottomed pot or Dutch oven, melt the unsalted butter over medium heat. Add the thinly sliced yellow onions along with 1 teaspoon salt and 1 teaspoon granulated sugar. Cook slowly, stirring occasionally, for about 40 minutes until the onions are deeply caramelized and golden brown. Add the minced garlic during the last few minutes of cooking to soften and develop flavor.
2. Deglaze with Wine: Pour in 1/2 cup dry red wine to deglaze the pot, scraping up the browned bits from the bottom with a wooden spoon. Let the wine reduce by half, about 5 minutes, concentrating its flavors.
3. Add Broths and Seasonings: Stir in 32 ounces low-sodium beef broth, 24 ounces low-sodium chicken broth, 1 tablespoon Worcestershire sauce, 2 sprigs of fresh thyme, and 1 bay leaf. Bring the mixture to a simmer, and let it cook uncovered for 30 minutes to allow the flavors to meld.
4. Finish the Soup: Remove the thyme sprigs and bay leaf. Stir in 1/2 tablespoon balsamic vinegar and season with a pinch of salt and freshly ground black pepper to taste. Keep the soup warm on low heat while preparing the bread and cheese topping.
5. Prepare the Bread: Preheat the oven to 350°F (175°C). Brush both sides of the 5 one-inch thick slices of French bread with 2 tablespoons olive oil. Place them on a baking sheet and toast in the oven until golden and slightly crisp, about 10 minutes, flipping halfway through.
6. Assemble and Broil: Ladle the hot soup into oven-safe bowls. Place one toasted bread slice on top of each bowl of soup. Generously sprinkle with a mixture of 1 1/2 cups shredded Gruyere, 1/4 cup shredded Mozzarella, and 2 tablespoons finely grated Parmesan cheeses. Place the bowls under the preheated broiler for 3-5 minutes or until the cheese is melted, bubbly, and golden brown.
7. Serve: Carefully remove the bowls from the oven (use oven mitts). Let cool slightly, then serve the rich and flavorful French Onion Soup immediately while hot.

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Notes

• Use dry red wine such as Cabernet Sauvignon or Merlot for best flavor in deglazing.
• Low-sodium broth allows better control over the soup’s saltiness.
• Room temperature cheese melts more evenly under the broiler.
• Oven-safe bowls are necessary to broil the cheese topping safely.
• Make sure to watch the soup closely under the broiler to prevent burning the cheese.

Keywords: French Onion Soup, caramelized onions, French bread, Gruyere cheese, comfort food, classic soup