Name: French Onion Soup with Gruyere and Mozzarella Recipe
Prep time: 15 min
Cook time: 1 h 15 min
Total time: 1 h 30 min
Cuisine: French
Ingredients: 4 tablespoons unsalted butter; 5 large yellow onions, thinly sliced; 1 teaspoon salt; 1 teaspoon granulated sugar; 2 cloves garlic, minced; 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; 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

French Onion Soup with Gruyere and Mozzarella Recipe is one of those cozy classics that feels like a warm hug in a bowl. The richness of the caramelized onions combined with those perfect melty cheeses—Gruyere and mozzarella—makes this soup irresistibly comforting. Whenever I crave something soothing on a chilly day, this recipe is my go-to because it’s simple yet elevates humble ingredients into something special.

What I love most about this French Onion Soup with Gruyere and Mozzarella Recipe is how the blend of cheeses adds a gooey texture and rich flavor that takes it beyond your average soup. It’s perfect for family dinners or impressing guests without fuss. Trust me, you’ll find yourself making this little masterpiece on repeat.

Ingredients You’ll Need

These ingredients come together beautifully to create that deep, layered flavor French onion soup is famous for. Don’t rush the onions—they’re the soul of this dish, and good quality cheese really lifts everything to the next level.

Unsalted butter: Perfect for sautéing onions without adding extra salt. Makes sure flavors stay balanced.
Yellow onions: Choose large and fresh for the best caramelization and sweetness.
Salt: Enhances the natural sugars in the onions while cooking.
Granulated sugar: Helps speed up the caramelization process without burning the onions.
Garlic: Adds a subtle kick and depth to the broth.
Dry red wine: Use a good sipping wine—this adds amazing richness.
Beef broth (low sodium): Provides the hearty base; low sodium lets you control seasoning.
Chicken broth (low sodium): Adds complexity and lightness to balance the beef broth.
Worcestershire sauce: A secret umami booster that deepens flavor.
Fresh thyme: Woody herb aroma is key to the classic taste.
Bay leaf: Adds subtle earthiness; just remember to remove before serving!
Balsamic vinegar: A splash heightens the onion’s caramel flavor with a slight tang.
Black pepper: Freshly ground adds a mild heat and aroma.
French bread slices: Thick and sturdy—perfect for soaking up that delicious broth while still holding its shape.
Olive oil: Used to toast the bread slices for crunch and flavor.
Gruyere cheese: The star cheese here with its nutty, slightly sweet flavor and great melting quality.
Mozzarella cheese: Adds milder creaminess and extra gooey texture.
Parmesan cheese: Just a sprinkle for an added sharp, salty punch.

Variations

I always encourage making this French Onion Soup with Gruyere and Mozzarella Recipe your own—tweak the cheeses or broth depending on what you have or prefer. I’ve found a few fun ways to switch it up without losing that classic flavor everyone loves.

Vegetarian version: Swap beef broth for mushroom or vegetable broth. I tried this for a friend who’s vegetarian, and it still packed tons of flavor.
Cheese blend variations: Sometimes I add a bit of sharp cheddar for extra tang or use all Gruyere if I want a richer taste.
Wine substitutions: If you’re out of red wine, dry sherry or even a splash of brandy works nicely.
Herb twists: Rosemary or marjoram in place of thyme can add an unexpected but wonderful layer of flavor.

How to Make French Onion Soup with Gruyere and Mozzarella Recipe

Step 1: Caramelize the Onions Slowly

First things first: slice those yellow onions nice and thin—trust me, even slices cook more evenly. Melt your unsalted butter in a large pot over medium heat, add the onions, a teaspoon of salt, and sugar. Now, here’s the trick: patience is your best friend. Stir frequently, letting the onions soften and slowly turn golden brown—not burnt! This takes about 30 to 40 minutes, but it’s what gives your soup that rich, sweet foundation no shortcut can replace.

Step 2: Deglaze and Build the Broth

Once the onions are caramelized to your liking, add minced garlic and cook for just a minute until fragrant. Pour in the dry red wine to deglaze the pan—that lovely red wine flavor will marry beautifully with the onions. Let it reduce for a few minutes, scraping up any browned bits stuck to the bottom. Then, stir in the beef and chicken broth, Worcestershire sauce, fresh thyme sprigs, and bay leaf. Bring everything to a gentle simmer and let it meld for about 30 minutes. Don’t forget to toss in a splash of balsamic vinegar right near the end for that subtle tang and complexity.

Step 3: Prepare the Bread and Cheese Topping

While the soup simmers, preheat your oven to 350°F (175°C). Brush the French bread slices with olive oil and toast them in the oven until golden and crisp. For me, this step gives the bread enough structure so it doesn’t turn into mush once it hits the soup. Then, mix your Gruyere and mozzarella cheeses together—this combo melts beautifully, creating that classic bubbly, golden topping we all crave.

Step 4: Assemble and Broil

Ladle the hot soup into oven-safe bowls. Place one or two toasted bread slices on top of each bowl, then cover generously with the cheese mixture. To really get that perfect golden bubbly top, pop the bowls under the broiler for 2-3 minutes—watch closely! As soon as the cheese is melted and golden with little bubbly spots, they’re ready. A quick sprinkling of finely grated Parmesan right out of the oven adds a lovely nutty finish. Just be careful handling hot bowls straight from the broiler!

How to Serve French Onion Soup with Gruyere and Mozzarella Recipe

The image shows six round white ramekins arranged on a rectangular metal baking tray with a worn surface. Each ramekin is filled with a layered dish topped with a golden brown melted cheese crust sprinkled with small green herb leaves. The cheese layer has browned edges, and some melted cheese has spilled down the sides. The dish inside has a rich, slightly textured surface suggesting multiple layers beneath the cheese topping. The baking tray rests on a white marbled surface. Photo taken with an iphone --ar 4:5 --v 7

Garnishes

I like to keep garnishes simple and classic. A little fresh thyme sprinkled on top adds a bright herbal pop and looks pretty too. Sometimes, a tiny drizzle of extra virgin olive oil adds richness just before serving. Freshly cracked black pepper is a must for me—gives a little peppery kick that balances the sweetness of the onions.

Side Dishes

This soup stands beautifully on its own but pairs so well with a crisp green salad tossed in a tangy vinaigrette to cut through the richness. I also often serve it alongside a simple roasted vegetable medley or a light charcuterie board if I’m entertaining and want to keep things casual yet elegant.

Creative Ways to Present

For special occasions, I like serving this French Onion Soup with Gruyere and Mozzarella Recipe in individual rustic crocks with handles. It feels extra cozy and inviting, perfect for a winter dinner party. You can also experiment with shaping the toasted bread into rounds or stars for a festive touch, especially around holidays.

Make Ahead and Storage

Storing Leftovers

I usually store leftover soup in airtight containers in the fridge for up to 3 days. I prefer to keep the toasted bread and cheese separate so you don’t lose that crisp texture. When you’re ready to eat, just reheat the soup and assemble the toppings fresh.

Freezing

This soup freezes quite well without the bread and cheese. Keep it in freezer-safe containers for up to 3 months. When thawed and reheated, it retains most of its richness. I recommend adding fresh bread and cheese when serving to keep that wonderful texture.

Reheating

Reheat your soup gently on the stovetop over medium-low heat, stirring occasionally until warmed through. Avoid boiling to keep those wonderful flavors intact. Then, assemble the toasted bread and cheese topping and broil again for that perfect finish just before serving.

FAQs

Can I make French Onion Soup with Gruyere and Mozzarella Recipe without red wine?

Absolutely! If you don’t want to use red wine, you can substitute with dry sherry, white wine, or even a splash of brandy. This still adds nice depth without overpowering the soup. Just keep in mind the flavor will be a little different but still delicious.
Why use both Gruyere and Mozzarella in this French Onion Soup recipe?

Gruyere brings that classic nutty, sweet flavor and melts gorgeously, while mozzarella adds creaminess and stringy goodness to the mix. Using both creates a gooey, luscious cheese topping that’s both flavorful and texturally satisfying.
How long does it take to caramelize onions properly for this soup?

Patience is key! It usually takes about 30 to 40 minutes on medium heat, stirring regularly. Rushing or turning the heat too high can cause burning rather than sweet caramelization. Take your time to get that deep golden color and rich flavor.
Can I prepare French Onion Soup with Gruyere and Mozzarella Recipe ahead of time?

Yes! The soup itself can be made a day or two in advance and reheated gently when you’re ready to serve. Just add the toasted bread and cheese topping fresh before broiling for best texture and flavor.

Final Thoughts

This French Onion Soup with Gruyere and Mozzarella Recipe holds a special place in my kitchen because of how it turns simple pantry staples into a soul-satisfying meal. It feels fancy enough to share with friends, yet easy enough for weeknight comfort food. I promise once you try it, it’ll become a recipe you’ll keep perfecting and sharing, just like I do. So go ahead—warm up your kitchen with this delight, and enjoy every cheesy, caramelized bite!