French Onion Soup with Fontina and Mozzarella

French onion soup with fontina and mozzarella combines caramelized onions, wine, broth, and roasted garlic with a cheesy, golden topping and crusty bread.

Also try Hawaiian chicken, perhaps paired with homemade onion rings. This crockpot chicken with cashews is delicious too.

Why You’ll Love It

Rich flavor: Slow-cooked onions, red wine, and roasted garlic build deep, complex flavor.
Cheesy topping: A combination of mozzarella and fontina adds a creamy, bubbly finish.
Comforting texture: Crisp bread and gooey cheese balance the savory soup base perfectly.
Make-ahead friendly: Caramelize the onions in advance to speed up prep.
Restaurant quality: Impressive presentation with easy, at-home ingredients.

French Onion Soup with Italian Cheese Ingredients

A complete list of ingredients and amounts can be found in the recipe card below.

Hearty Italian bread: Holds up well under broiled cheese and adds texture.
Beef broth: Forms a rich, savory base.
Red wine: Adds depth and a touch of acidity.
Sweet onions and red onions: Caramelize beautifully and provide the classic onion flavor.
Garlic: Roasted to mellow sweetness, then blended into the soup.
Fontina cheese: Melts smoothly and adds creaminess.
Mozzarella cheese: Provides stretch and that golden broiled finish.
Chicken bouillon: Intensifies the savory broth.
Fresh thyme: Adds a subtle, earthy note.
Butter and olive oil: Help caramelize the onions and enrich the base.
Cornstarch: Thickens the broth if preferred.
Onion powder and brown sugar: Enhance sweetness and deepen onion flavor.

How to Make Fontina and Mozzarella Onion Soup

For more detailed instructions with weights and measurements, jump to the printable recipe card.

Roast the garlic: Slice the top off the garlic head, drizzle with olive oil, and wrap in foil. Roast until tender.
Caramelize the onions: Cook sliced onions in butter and oil with brown sugar, salt, and pepper until golden and soft.
Build the base: Add roasted garlic, red wine, thyme, beef broth, and bouillon. Simmer and adjust seasoning.
Optional thickening: Add a cornstarch slurry for a thicker broth, if liked.
Toast and prep bread: Cube the bread and set aside.
Assemble the soup: Pour soup into oven-safe bowls, top with bread, mozzarella and fontina.
Broil until golden: Place under the broiler until cheese is melted and bubbling.

Substitutions and Variations

Swap the cheese: Gruyère or provolone can replace the fontina or mozzarella.
Use vegetable broth: For a meat-free version, swap beef broth for vegetable broth.
Skip the wine: Use extra broth if you prefer to avoid alcohol.
Try a different herb: Use rosemary or bay leaf in place of thyme for a new twist.

Serving Suggestions

With vegetables: Enjoy roasted artichokes alongside your soup, or perhaps some roasted acorn squash.
With bread: Italian bread such as focaccia or even mushroom focaccia would be good, since the cheeses in this soup are Italian too.
With a salad: Enjoy a charred zucchini salad on the side.
With a glass of wine: Choose something medium bodied and earthy to go with your onion soup, perhaps a Beaujolais or Pinot Noir. If you prefer white wine, consider Viognier or a crisp Sauvignon Blanc.

How to Store French Onion Soup

Store: Keep leftovers in an airtight container in the refrigerator and use within 3 to 4 days.
Freeze: You can freeze it in an airtight container for up to 3 months (add the bread and cheese fresh, after thawing).
Thaw: Defrost it in the refrigerator overnight.
Reheat: You can warm the soup back up in a pan on the stove or in the microwave.