French Onion Soup with Fontina and Mozzarella

Ingredients

• 1 loafhearty Italian-style bread (a rosemary Italian loaf works well)
• 946 ml (4 cups)beef broth
• 118 ml (½ cup)red wine
• 2sweet onions, thinly sliced
• 2red onions, thinly sliced
• 1 bulbgarlic
• 142 g (5 oz)Fontina cheese, freshly shredded
• 4 slicesmozzarella cheese
• 2 cubeschicken bouillon
• 2 sprigsfresh thyme
• 30 ml (2 tablespoons)butter
• 30 ml (2 tablespoons)olive oil
• 22.5 ml (1½ tablespoons)cornflour
• 1 teaspoononion powder
• 1 teaspoonbrown sugar
• to tastesalt
• to tasteblack pepper

Instructions

1. 1

   Preheat the oven

   Heat the oven to 204°C.

2. 2

   Roast the garlic

   Cut the top from the garlic bulb to expose the cloves. Set it on a square of foil, drizzle a generous amount of olive oil over the exposed cloves, and season lightly with salt and pepper. Bring the foil corners together and twist them into a snug parcel over the garlic. Roast for 30 minutes.

3. 3

   Start the onions

   Put the butter and olive oil in a heavy-based pot. Add the onions and brown sugar, then season with salt and pepper.

4. 4

   Caramelise the onions

   Cook over a medium-low heat for at least 30 minutes, stirring occasionally, until the onions are soft and caramelised.

5. 5

   Cube the bread

   While the onions cook, cut the bread into bite-sized cubes and set aside.

6. 6

   Add roasted garlic

   Once the onions are soft and caramelised, add 5 roasted garlic cloves and mix them in.

7. 7

   Add wine and broth

   Pour in the red wine and add the fresh thyme. Simmer for a couple of minutes, then add the beef broth and chicken bouillon cubes.

8. 8

   Simmer the soup

   Simmer for 15 minutes. Taste the soup and adjust the seasonings as needed.

9. 9

   Thicken if desired

   For a thicker soup, mix ¼ cup of water with 2 tablespoons of cornstarch to make a slurry. Pour half into the soup, stir, and simmer for a minute. Skip this step if you do not want a thicker soup.

10. 10

    Fill the bowls

    Divide the soup between 4 oven-safe soup bowls.

11. 11

    Add the toppings

    Cover each bowl with a layer of chopped bread, then add a slice of mozzarella and one quarter of the Fontina.

12. 12

    Broil until golden

    Switch on the oven grill. Put the bowls together on a baking sheet and place them under the grill. Watch closely so the topping does not burn; remove the bowls when the cheese is melted, golden and bubbling.

What is French onion soup?

French onion soup is a classic French dish built around onions cooked until sweet and deeply savoury, served in broth with bread and melted cheese. This version layers sweet and red onions with red wine, beef broth and roasted garlic.

The long, gentle cooking gives the onions time to caramelise, while Fontina and mozzarella melt over the bread for a soft, gooey finish.

Nutrition and macros by portion

The nutrition label shows one serving as written: 894 calories, 38g protein, 111g carbs, 31g fat.

The bread supplies much of the carbohydrate, while the butter, olive oil and cheese contribute much of the fat. Protein comes mainly from the beef broth and cheeses. For a more balanced plate, serve a bowl with a green salad or another vegetable side.

Let the onions take their time

Low heat: Cook the onions for at least 30 minutes, stirring now and then. They should become soft and browned rather than scorching at the edges.

Brown sugar: It adds sweetness as the onions cook, but the onions still need time on the heat to develop their flavour.

Roasted garlic adds depth

Foil parcel: Exposing the cloves and wrapping the bulb helps it roast without drying out. The recipe uses 5 roasted cloves in the soup, so keep the rest for another use.

Olive oil: Drizzle it over the exposed cloves before roasting, and season them lightly with salt and pepper as directed.

Build flavour in stages

Red wine: Let it simmer with the thyme for a couple of minutes before adding the broth and bouillon. This gives the wine a moment to mingle with the caramelised onions.

Seasoning: Taste after the 15-minute simmer and adjust salt, pepper or other seasonings to your preference.

Choose your soup texture

Cornflour slurry: The recipe makes this optional, so you can leave it out for a thinner broth. If using it, add half first, simmer for a minute and check the consistency before adding more.

Bread topping: Add the bread just before the cheese and grilling. This lets it sit on the soup and take on some broth while the cheese melts over it.

Watch the grill closely

Oven-safe bowls: Divide the soup among 4 bowls that can withstand the heat, and set them on a baking sheet for easier handling.

Golden finish: Stay nearby while grilling. Take the bowls out as soon as the cheese is melted, golden and bubbling so the topping does not burn.

What to serve alongside

Fresh contrast: A simple green salad with a sharp vinaigrette balances the rich broth and melted cheese.

Keep it simple: The bread and cheese make the soup substantial, so a light side of dressed leaves or steamed green vegetables is usually enough.

Recipe notes & tips

• Slice the onions evenly so they soften at a similar pace.
• Keep the heat at medium-low while caramelising to help prevent the onions catching.
• Set the garlic parcel on a tray in case oil escapes from the foil.
• Use a baking sheet to move the filled bowls in and out of the oven safely.
• Taste the broth before adding more salt, as the bouillon cubes can be salty.

Variations

• Use vegetable broth: Replace the beef broth with vegetable broth for a different base.
• Try another melting cheese: Use a similar quantity of Gruyère or Emmental in place of the Fontina.
• Change the bread: Choose a sturdy loaf that can hold its shape under the broth and cheese.
• Add extra herbs: Include a little chopped parsley at the table for a fresh finish.
• Skip the thickener: Leave out the cornflour slurry for a lighter, brothier soup.

Common mistakes to avoid

• Rushing the onions: They will lack the deep sweet flavour; keep the heat medium-low and give them at least 30 minutes.
• Letting the onions catch: Stir occasionally and lower the heat if they start browning too quickly.
• Adding the cheese too early: Put the bread and cheeses on only after dividing the soup into oven-safe bowls.
• Walking away from the grill: The topping can burn quickly; watch until the cheese is just golden and bubbling.
• Adding all the slurry at once: The soup may become thicker than intended; add half, simmer, and check first.

How to store

Cool leftover soup promptly and store it covered in the fridge for up to 3 days. Keep any bread and cheese topping separate if possible, then reheat the soup on the hob and add fresh toppings before grilling. Reheat only once, until steaming hot throughout.

Frequently asked questions