French Onion Soup is a classic comfort food that’s all about deep, caramelized onions swimming in a rich, beefy broth. The best part? It’s topped with a golden, bubbly layer of melted cheese resting on a crusty toasted baguette slice. This soup feels cozy and warm with every spoonful, making it a perfect dish for chilly evenings.
I love making this soup slowly so the onions get that sweet, golden-brown flavor that really makes the difference. It takes a bit of time, but it’s worth every minute because the taste is so rich and satisfying. I usually stir the onions patiently while they cook and smell that amazing aroma fill the kitchen—honestly, it’s comforting just to make it.
To serve, I pile on plenty of cheese and make sure the bread soaks up just enough of the broth before melting the cheese under the broiler. I like to eat it right out of the oven when the top is all bubbly and slightly crispy. It’s the kind of meal that feels like a warm hug on a cold day, and it’s always a crowd-pleaser whenever I serve it to friends and family.
Key Ingredients & Substitutions
Yellow Onions: These onions caramelize beautifully, giving the soup its deep, sweet flavor. If you can’t find yellow onions, sweet onions or even Vidalia onions work well too.
Butter & Olive Oil: The combination helps caramelize the onions evenly. You can use all olive oil for a lighter option, or all butter for richness.
Beef Broth: I recommend using homemade or low-sodium beef broth for the best flavor and control over salt. For a vegetarian version, use mushroom or vegetable broth.
Gruyère Cheese: This cheese melts wonderfully and adds a nutty flavor. If you can’t find Gruyère, Swiss or even mozzarella are good substitutes.
Baguette: A nice crusty baguette is key to soaking up the soup and holding the cheese. Toast it well so it doesn’t get soggy too quickly.
How Can I Perfectly Caramelize Onions Without Burning Them?
Caramelizing onions is the heart of this soup, but it takes patience and attention.
- Cook onions on medium-low heat to allow their natural sugars to develop slowly without burning.
- Stir frequently—about every 5 minutes—to prevent sticking and even cooking.
- Add a pinch of sugar halfway through to encourage caramelization and deepen sweetness.
- If onions start sticking too much, add a splash of water or broth to deglaze the pan.
Taking your time with this step creates the rich, sweet base that makes your French Onion Soup taste amazing.
Equipment You’ll Need
- Large heavy-bottomed pot or Dutch oven – I like this because it heats evenly and can handle long simmering and caramelizing.
- Wooden spoon – perfect for stirring the onions and scraping the browned bits from the bottom without scratching.
- Baking sheet – for toasting the baguette slices until crispy.
- Oven-safe soup bowls – so you can melt the cheese right on top under the broiler.
- Broiler – to quickly melt and brown the cheese for that bubbly, golden topping.
Flavor Variations & Add-Ins
- Use Swiss or mozzarella cheese instead of Gruyère if you prefer a different flavor or for easier availability.
- Add a splash of balsamic vinegar during caramelization for a deeper, tangy sweetness.
- Stir in cooked mushrooms or sliced leeks for extra earthy flavor and texture.
- Try using chicken or vegetable broth for a lighter, different taste option.
How to Make French Onion Soup
Ingredients You’ll Need:
- 6 large yellow onions, thinly sliced
- 4 tbsp unsalted butter
- 2 tbsp olive oil
- 1 tsp sugar
- 2 cloves garlic, minced
- 8 cups beef broth (preferably homemade or low sodium)
- 1/2 cup dry white wine
- 2 tsp fresh thyme leaves (or 1 tsp dried thyme)
- 1 bay leaf
- Salt and freshly ground black pepper, to taste
- Baguette, sliced into 1/2 inch thick rounds
- 2 cups grated Gruyère cheese (or Swiss cheese)
How Much Time Will You Need?
This French Onion Soup takes about 1 hour 30 minutes total: around 50 minutes to slowly caramelize the onions, plus 30 minutes to simmer the soup. Toasting the bread and broiling the cheese will take about 10 minutes more. It’s worth the time for that rich, comforting flavor!
Step-by-Step Instructions:
1. Caramelize the Onions
In a large heavy-bottomed pot or Dutch oven, melt the butter with olive oil over medium heat. Add the sliced onions and stir well to coat them with the butter and oil. Cook the onions slowly, stirring often, until they turn deeply golden and caramelized. This takes about 40-50 minutes. Sprinkle the sugar halfway through to help the onions caramelize nicely.
2. Make the Soup Base
Add the minced garlic to the onions and cook for another minute until fragrant. Pour in the white wine and scrape the bottom of the pot to loosen all those tasty browned bits. Add the beef broth, thyme, and bay leaf. Bring the soup to a gentle simmer, then lower the heat and cook uncovered for 30 minutes. Season with salt and pepper to taste before removing the bay leaf.
3. Prepare the Cheese Toasts and Broil
While the soup simmers, preheat your oven’s broiler. Arrange the baguette slices on a baking sheet and toast them under the broiler until golden brown on both sides, about 1-2 minutes per side. Ladle the hot soup into oven-safe bowls, top each with one or two baguette slices, and generously cover the bread with grated Gruyère cheese. Place the bowls on a baking sheet and broil until the cheese is melted, bubbly, and golden, about 3-5 minutes. Be careful removing the hot bowls from the oven!
4. Serve and Enjoy
Optionally sprinkle some chopped fresh parsley for a pop of color and freshness. Serve immediately with a spoon and enjoy the warm, rich flavors of your homemade French Onion Soup.
Can I Use Different Types of Onions?
Yes! Yellow onions work best for their sweetness and caramelizing ability, but you can also use sweet onions or even a mix of onions for a slightly different flavor. Just adjust cooking time as needed.
How Should I Store Leftover French Onion Soup?
Store leftovers in an airtight container in the fridge for up to 3 days. Reheat gently on the stove or in the microwave. Add fresh bread and cheese before broiling again for the best experience.
Can I Make This Soup Ahead of Time?
Absolutely! You can caramelize the onions and make the soup up to 2 days ahead. When ready to serve, reheat the soup and prepare the cheese toasts fresh for melting under the broiler.
What If I Don’t Have Gruyère Cheese?
No problem! Swiss cheese is a great substitute, or you can use mozzarella for a milder flavor. Just make sure it melts well for that classic bubbly topping.
