French Onion Soup is a classic dish that’s all about rich, caramelized onions swimming in a warm, flavorful broth, topped with crusty bread and melted cheese. It’s simple but feels special, with deep, sweet onion flavors and that gooey, cheesy crust that’s impossible to resist.
I love making this soup when I want something cozy and a little bit fancy without a lot of fuss. One tip I always follow is to cook the onions slowly and patiently—they take their time to turn golden and develop that amazing sweetness that makes the soup so good. It’s worth the wait!
Whenever I serve French Onion Soup, I like to pair it with a fresh green salad or just enjoy it as a meal on its own. It’s the perfect dish for chilly evenings or when you need a little comfort in a bowl. Plus, the cheesy bread topping always brings smiles all around the table.
Key Ingredients & Substitutions
Yellow Onions: These are best because they caramelize well and bring natural sweetness. If you don’t have yellow onions, sweet onions or even Vidalia can work too.
Butter & Olive Oil: Butter adds richness, and oil helps prevent burning. If you want a dairy-free version, use all olive oil or another neutral oil.
Beef Broth: It gives deep flavor. You can swap in vegetable broth for a vegetarian option, but the taste will be lighter. Combining beef and chicken broth keeps it balanced if you want.
Gruyère Cheese: Classic choice for melting and flavor. Swiss cheese is a good substitute. For a milder taste, mozzarella works, but it won’t brown quite the same.
Bread: A crusty baguette is ideal to soak up the soup without getting soggy too fast. If you don’t have baguette, any sturdy crusty bread will do.
How Do You Get Perfectly Caramelized Onions Without Burning Them?
Caramelizing onions slowly is key to unlocking their rich, sweet flavor. Here’s how to do it:
- Cook onions over medium heat, stirring often to avoid sticking.
- Be patient—it takes about 45 minutes total. If they start to burn, lower the heat.
- Add a pinch of sugar early on to boost caramelization without needing extra heat.
- If they stick to the pan, add a splash of water or broth to loosen the fond (browned bits).
Take your time here; this step makes all the difference in flavor and color for your soup!
Equipment You’ll Need
- Large heavy-bottomed pot or Dutch oven – I recommend this because it heats evenly and helps prevent burning the onions.
- Wooden spoon – perfect for scraping up browned bits and stirring the onions gently.
- Baking sheet – for toasting the bread slices until golden and crispy.
- Broiler-safe bowls – so you can melt the cheese directly in the oven without transferring to another dish.
- Oven or broiler – for finishing the cheese topping until bubbly and lightly browned.
Flavor Variations & Add-Ins
- Use caramelized shallots instead of onions for a sweeter, more delicate flavor.
- Swap Gruyère for Swiss or mozzarella if you prefer a different melt or taste profile.
- Add a splash of balsamic vinegar while cooking the onions for extra depth and tang.
- Include sautéed mushrooms or cooked bacon bits to make it more hearty and flavorful.
How to Make French Onion Soup
Ingredients You’ll Need:
- 4 large yellow onions, thinly sliced
- 3 tablespoons unsalted butter
- 1 tablespoon olive oil
- 1 teaspoon salt
- ½ teaspoon sugar
- 4 cups beef broth (or a mix of beef and chicken broth)
- 1 cup dry white wine (optional)
- 2 cloves garlic, minced
- 2 sprigs fresh thyme (or 1 teaspoon dried thyme)
- 1 bay leaf
- Salt and freshly ground black pepper, to taste
- 1 baguette or crusty French bread, sliced into ½-inch thick rounds
- 2 cups grated Gruyère cheese (or Swiss cheese)
- Fresh thyme leaves, for garnish
How Much Time Will You Need?
This recipe takes about 1 hour and 15 minutes in total. You’ll spend around 55 minutes slowly caramelizing the onions and simmering the soup, plus 10-15 minutes for prepping, toasting the bread, broiling the cheese, and final assembly.
Step-by-Step Instructions:
1. Caramelize the Onions
Start by melting the butter with olive oil in a large heavy-bottomed pot over medium heat. Add the sliced onions and salt, then cook, stirring often, until they soften and start to turn brown, about 20 minutes. Sprinkle sugar on the onions to help caramelize them, and keep cooking, stirring frequently, for another 25-30 minutes until deeply golden and sweet. Be patient and watch the heat to prevent burning.
2. Add Flavorings and Simmer
Stir in the minced garlic and cook for another minute. Pour in the white wine to deglaze the pot—scrape any browned bits from the bottom and let the wine reduce for 3-4 minutes. Then add the beef broth, thyme sprigs, and bay leaf. Bring the soup to a boil, then lower to a simmer and cook uncovered for 30 minutes to let all the flavors meld together. Season with salt and pepper to your taste.
3. Toast Bread and Add Cheese
While the soup simmers, set your oven’s broiler on high. Place the baguette slices on a baking sheet and toast them under the broiler for 1-2 minutes per side until golden and slightly crispy. Remove the thyme sprigs and bay leaf from the soup, then ladle the soup into oven-safe bowls. Lay one or two toasted bread slices on each bowl, and cover generously with grated Gruyère cheese. Place the bowls under the broiler carefully and cook for 2-3 minutes until the cheese melts, bubbles, and turns golden brown. Keep a close eye so the cheese doesn’t burn. Garnish with fresh thyme leaves and serve immediately.
Can I Use Frozen Onions for This Soup?
It’s best to use fresh onions for caramelizing since frozen ones release extra moisture and won’t brown properly. If you only have frozen, thaw and drain them well before cooking, but expect a less rich flavor.
Can I Skip the Wine?
Absolutely! The wine adds depth, but you can omit it if you prefer or don’t have any. Just substitute with a bit of extra broth or a splash of vinegar for a touch of acidity.
How Should I Store Leftovers?
Keep any leftover soup in an airtight container in the fridge for up to 3 days. To reheat, warm gently on the stove. Toast fresh bread and re-melt cheese before serving for the best experience.
What’s a Good Bread Alternative?
If you don’t have baguette, use any sturdy, crusty bread that holds up well when soaked, such as sourdough or a rustic country loaf. Avoid softer bread that sogs too quickly.