Ultimate French Onion Soup: Comfort in Every Bite

Ingredients

• 75 ml (5 tablespoons)olive oil
• 15 g (1 tablespoon)butter
• 1.36 kg (about 8 cups; approximately 3 pounds)onions, thinly sliced
• 3 clovesgarlic, minced
• 120 ml (½ cup)apple cider vinegar or dry apple juice
• 1.89 litres (64 ounces)beef broth or vegetable broth
• to tastesalt and pepper
• 24 slices, 1.3 cm thick (½ inch)French baguette
• about 85 g (¾ cup)Gruyère or Swiss cheese, shredded

Instructions

1. 1

   Caramelise onions

   Heat the olive oil and butter in a large pot over medium heat. Add the sliced onions and cook slowly, stirring occasionally, for about 30–40 minutes, until golden brown and caramelised.

2. 2

   Deglaze the pot

   Stir in the minced garlic and cook for 1 minute. Add the apple cider vinegar or dry apple juice, scraping up any browned bits from the bottom of the pot.

3. 3

   Simmer the soup

   Pour in the beef or vegetable broth and season with salt and pepper. Bring the soup to a gentle boil, then lower the heat and simmer for about 30 minutes.

4. 4

   Toast the baguette

   Preheat the oven broiler. Arrange the baguette slices on a baking sheet and toast until lightly golden.

5. 5

   Top and broil

   Ladle the hot soup into oven-safe bowls. Place toasted baguette slices on top and sprinkle with shredded cheese. Broil for 3–5 minutes, until the cheese is bubbly and slightly browned.

What is French onion soup?

French onion soup is a classic French dish built around onions cooked until deeply golden, then simmered in broth. Toasted bread and melted cheese make the top hearty and savoury.

This version uses a splash of apple cider vinegar or dry apple juice to lift the rich broth. The baguette and Gruyère or Swiss finish it in the familiar gratin style.

Nutrition and macros by portion

The nutrition label shows one serving as written: 450 calories, 14g protein, 52g carbs, 20g fat.

The onions and baguette provide most of the carbohydrates, while olive oil, butter and cheese contribute much of the fat. The broth and cheese provide some protein, with the exact balance depending on the broth and cheese chosen. Pair a bowl with a green salad or other vegetables for a more balanced plate.

Give the onions time

Onions: cook them slowly over medium heat, stirring from time to time, for the full 30–40 minutes. They should become soft and golden brown rather than just translucent.

Pot: use a large one so the onions are easier to stir as they soften and release moisture. Scrape the base when adding the vinegar or juice to lift the browned flavour into the soup.

Build a savoury broth

Broth: beef broth gives the soup a robust flavour, while vegetable broth offers a meat-free alternative. Both work with the sweet onions and toasted bread.

Seasoning: add salt and pepper with the broth, then taste after simmering. Broths vary in saltiness, so adjust with care.

Toast before topping

Baguette: toast the slices lightly before they go on the soup. This helps them hold their shape under the hot broth and cheese.

Cheese: scatter it over the bread so it melts across the topping. Gruyère has a distinct savoury character; Swiss cheese is another option in this recipe.

Watch the broiler

Broiling: keep the bowls under the broiler for 3–5 minutes, until the cheese bubbles and begins to brown. The topping can go from golden to overly dark quickly, so keep an eye on it.

Bowls: use oven-safe bowls and handle them carefully when serving, as both the soup and the dishes will be very hot.

Make it a meal

Serve the soup hot, straight after the cheese has melted. A crisp green salad or simply dressed leaves make a fresh contrast to the rich broth and cheesy bread.

For a more substantial meal, serve extra baguette on the side. The soup is also filling on its own, especially with several topped slices in each bowl.

Recipe notes & tips

• Slice the onions evenly so they cook at a similar pace.
• Stir the onions occasionally and scrape the pot if browned bits start to build up.
• Use oven-safe bowls for the final broiling step.
• Toast the baguette until lightly golden rather than very dark.
• Broil the topped bowls close to serving time so the bread and cheese are at their best.

Variations

• Choose vegetable broth: use it instead of beef broth for a meat-free version.
• Swap the cheese: use Gruyère or Swiss, as listed, to suit your preference.
• Use dry apple juice: choose it instead of apple cider vinegar for a gentler tang.
• Add fresh herbs: finish each bowl with a little chopped parsley for a fresh note.
• Serve extra bread: offer additional toasted baguette on the side for a heartier meal.

Common mistakes to avoid

• Rushing the onions: they need 30–40 minutes to caramelise; keep the heat at medium and cook them slowly.
• Letting the onions catch: stir occasionally and lower the heat if they start browning too quickly.
• Skipping the scrape: lift the browned bits with the vinegar or juice so they flavour the broth.
• Using non-oven-safe bowls: check the bowls before filling and broiling the soup.
• Leaving the broiler unattended: watch closely during the 3–5 minutes, as the cheese can brown quickly.

How to store

Store leftover soup without the bread and cheese in a covered container in the fridge for up to 3 days. Reheat it until hot, then add toasted baguette and cheese and broil just before serving.

Frequently asked questions