French Onion Soup is a timeless classic that wraps you in warmth with its rich, caramelized sweetness and savory depth. Each spoonful delivers a perfect harmony of tender onions, aromatic herbs, and a golden, gooey cheese topping that melts into every bite. In just under two hours, you’ll create a dish that feels like a cozy hug on a chilly evening.

The velvety broth, infused with a hint of white wine, pairs beautifully with the crunch of toasted baguette slices. This recipe’s simplicity lets the bold, comforting flavors shine, making it an impressive yet approachable meal for any occasion. It’s a bowl of pure indulgence that’s worth every minute of simmering.

Ingredients for French Onion Soup

6 tablespoons extra-virgin olive oil
3 pounds medium yellow onions (halved and thinly sliced)
¾ teaspoon sea salt
1½ tablespoons balsamic vinegar
1½ tablespoons tamari (or substitute soy sauce)
1½ tablespoons fresh thyme leaves (or 1½ teaspoons dried thyme)
3 garlic cloves, minced
3 tablespoons all-purpose white flour
1 cup dry white wine (substitute with additional broth if preferred)
6 cups vegetable broth
Freshly ground black pepper (to taste)

Topping:

Baguette slices (about ½ inch thick)
Gruyère cheese, aged cheddar, and/or Parmesan cheese (shredded or sliced)
Fresh thyme (for garnish)
Pinch of red pepper flakes (optional, for a hint of spice)

Step-by-Step Instructions

Cook the onions: Heat the olive oil in a large pot or Dutch oven over medium heat. Add the onions, salt, and several grinds of black pepper. Toss to combine. Reduce the heat to low and cook for about 40 minutes, stirring every few minutes, until the onions are very soft.
Caramelize the onions: Increase the heat to medium and cook for 15 to 20 more minutes, stirring often, until the onions are golden brown.
Add flavorings: Stir in the balsamic vinegar, tamari, thyme, and garlic. Sprinkle the flour over the onions, stir, and cook for 2 minutes to thicken.
Deglaze with wine: Pour in the white wine and cook for 2 minutes, or until the liquid has mostly evaporated.
Simmer the soup: Add the vegetable broth and bring to a simmer over medium heat. Cook for 30 minutes, stirring occasionally.
Prepare the topping: While the soup simmers, preheat the oven to 450°F. Line a baking sheet with parchment paper. Place the baguette slices on the sheet and top with your choice of cheese. Bake for 8 to 10 minutes, or until the bread is toasted and the cheese is melted and bubbly.
Serve: Ladle the soup into ramekins or bowls. Top each with a toasted baguette slice, a sprinkle of fresh thyme, and a pinch of red pepper flakes if desired. Enjoy hot!

Perfect Pairings: Serving Suggestions

French Onion Soup is a hearty dish that pairs beautifully with a crisp green salad or a side of roasted vegetables. For a complete meal, serve it alongside a glass of the same dry white wine used in the recipe. Pro tip: Add a dollop of Dijon mustard to your salad dressing for a tangy complement to the soup’s rich flavors.

Storing and Reheating Like a Pro

Store leftover soup in an airtight container in the fridge for up to 3 days. To reheat, warm it gently on the stovetop over medium heat, stirring occasionally. Note: Keep the toasted baguette and cheese separate until ready to serve to maintain their crispiness. For freezing, omit the bread and cheese, and freeze the soup for up to 2 months.

Time-Saving Tips for Busy Cooks

To cut down on prep time, use a mandoline slicer for the onions—it’s faster and ensures even slices. If you’re short on time, caramelize the onions in advance and store them in the fridge for up to 2 days. Bonus tip: Use pre-sliced baguette and shredded cheese to speed up the topping process.

Recipe Variations to Mix It Up

For a twist, try using red onions or shallots for a slightly sweeter flavor. Swap the Gruyère cheese for smoked Gouda or mozzarella for a different melt-in-your-mouth experience. If you’re gluten-free, substitute the flour with a gluten-free alternative and use a gluten-free baguette for the topping.

Essential Equipment for Success

A heavy-bottomed Dutch oven is ideal for even heat distribution when caramelizing the onions. A sharp chef’s knife or mandoline slicer will make quick work of the onions. Don’t forget oven-safe ramekins or bowls for serving—they’re perfect for broiling the cheesy topping right before serving.