Classic French Onion Soup

This French Onion Soup is a timeless classic that beautifully combines buttery caramelized onions, a rich and savory broth, and cheesy toasted bread. Inspired by Julia Child’s legendary version, this soup is deeply flavorful and offers a comforting warmth that makes it perfect for chilly evenings or when you want a soothing meal.

I first made this on a rainy weekend and was amazed at how the humble ingredients transformed into something so rich and satisfying. Now it has become my go-to soup whenever I want something cozy and special that reminds me of classic French cooking.

Ingredients

• Olive oil: helps sauté and caramelize the onions with a light base flavor. Choose extra virgin for best aroma
• Unsalted butter: adds richness and aids in browning the onions evenly
• Yellow onions: thickly sliced for sweetness and soft texture. Select large firm onions with tight skins
• Sugar: enhances caramelization and balances the savory flavors with natural sweetness
• Salt: draws moisture from onions and seasons the broth. Kosher salt or sea salt preferred for even seasoning
• All-purpose flour: used to make a roux which thickens the soup. Fresh flour ensures smoothness
• Beef broth: forms the hearty base of the soup. Low sodium options let you control the salt perfectly
• Red wine: lends acidity and complexity. Choose dry wines like Pinot Noir or Merlot for best results
• Bay leaves and thyme: classic aromatics that infuse subtle herbal notes
• Cognac: adds depth and a slight warmth. Brandy is a good substitute or can be omitted if preferred
• French baguette: sturdy enough to hold up when toasted and placed on the soup without getting soggy too fast
• Gruyere cheese: essential for luxurious melting and nutty flavor. Pick a good quality, fresh block to shred
• Parmesan cheese: adds sharpness and a nice topping contrast

Instructions

Caramelize the Onions:

In a large heavy pot such as a Dutch oven, warm the olive oil and 2 tablespoons of butter over medium heat until melted. Add the sliced onions and stir to coat them in fat. Cover the pot partially and let the onions cook gently for 20 minutes, stirring occasionally to avoid burning, until they become translucent.

Deepen the Flavor with Sugar and Salt:

Remove the lid after 20 minutes and sprinkle the sugar and salt over the onions. Continue cooking uncovered for 40 minutes, stirring frequently. This slow caramelization is key as it transforms the onions into a deep golden brown and brings out their natural sweetness.

Make a Roux:

Add the flour and remaining 1 tablespoon of butter to the onions and stir continuously. Cook for about 2 to 3 minutes to eliminate the raw flour taste. This roux will help thicken the soup nicely.

Deglaze the Pot:

Pour in 1 cup of beef broth and stir well to scrape up all browned bits from the bottom of the pot. Cook for about 1 minute until the liquid almost evaporates which intensifies the flavor.

Add Broth, Wine, and Herbs:

Add the rest of the beef broth along with the red wine. Toss in the bay leaves and thyme sprigs. Bring the soup to a boil and then reduce the heat to a simmer. Let it cook uncovered for 30 minutes so all the flavors meld.

Season and Add Cognac:

Remove the herb sprigs and taste the soup. Adjust seasoning with salt and pepper as needed. Stir in the cognac last to add a subtle warmth and complexity.

Prepare the Cheese and Bread Topping:

Preheat your oven to 350 degrees Fahrenheit or 177 degrees Celsius. Lightly drizzle olive oil on the baguette slices and toast them under the broiler for about 30 seconds to 1 minute per side until golden and crispy.

Assemble and Melt:

Ladle the soup into oven safe bowls or keep it in the pot. Sprinkle about a cup of shredded Gruyere cheese over the soup first, lay the toasted bread slices on top, and then cover them evenly with the remaining Gruyere and Parmesan cheese.

Bake and Serve:

Place the bowls or pot in the oven and bake for 20 to 25 minutes until the cheese melts and starts to bubble and brown beautifully. Serve hot for the best gooey comforting experience.

One of my favorite ingredients is the slow-cooked onions. Their transformation from sharp raw slices to luscious, sweet, golden morsels is always a little magic moment for me while cooking. This soup also reminds me of family dinners when everyone would gather around the table on cold winter nights sharing stories over a bubbling pot of this very soup.

Storage Tips

Store leftovers in airtight containers in the refrigerator for up to four days. Reheat gently on the stove to avoid overcooking the cheese topping. For longer storage, freeze the soup without the bread and cheese and add fresh toasted bread and cheese after thawing and reheating.

Ingredient Substitutions

If you prefer a vegetarian version, swap the beef broth for a rich mushroom or vegetable broth and skip the cognac or use a splash of sherry vinegar instead. You can also use Swiss cheese if Gruyere is unavailable although it won’t have quite the same nutty depth.

Serving Suggestions

This soup makes a complete meal on its own but pairs wonderfully with a simple green salad dressed in vinaigrette or some roasted root vegetables to keep the cozy winter vibe. A crisp white wine or a light red complements the flavors nicely.

Enjoy warm and comforting French Onion Soup, perfect for chilly nights. Serve with extra crusty bread and a glass of wine.

Common Questions About Recipes

→ What type of onions work best for this dish?

Yellow onions are preferred for their natural sweetness and bright flavor, though shallots can add a balanced sweetness and depth.

→ Can I use different cheese varieties for topping?

Gruyere cheese is ideal for its smooth melting qualities and rich taste, with Parmesan added for sharpness and extra flavor.

→ How is the broth flavored in this preparation?

The broth is enriched with low-sodium beef broth, dry red wine, bay leaves, thyme, and a splash of cognac for warmth.

→ Is there a recommended way to prepare the bread topping?

Lightly brushed with olive oil, bread slices are toasted under the broiler before layering onto the soup to add texture and prevent sogginess.

→ How long should the onions be caramelized?

Onions are cooked covered for 20 minutes at medium heat, then uncovered and stirred for an additional 40 minutes until deeply golden and sweet.

→ Can I omit the cognac if unavailable?

Yes, cognac can be replaced with brandy or skipped entirely without losing the core flavors of the dish.