French Onion Soup

This classic french onion soup  is made with caramelized onions simmered in beef broth, wine and brandy. Because of this, it has both intense savory flavor from the liquids as well as natural sweetness from the softened onions. 

Traditionally, yellow onions are used since they contain sugar which increases when slowly cooked. Through slow cooking, the onions caramelize into soft, sweet bundles of flavor. 

Furthermore, at first the consistency is quite brothy but then it thickens some as bread placed on top soaks up liquid over time. Small amount of extra sugar enhances the onions’ inherent sweet taste.

French Onion Soup Ingredients 

• Yellow onions
• Butter
• Garlic
• Flour
• Dry white wine
• Beef stock (or vegetable stock)
• Worcestershire sauce
• Bay leaf
• Fresh thyme
• Fine sea salt
• Freshly-cracked black pepper
• Baguette
• Cheese (Gruyère or Swiss)

How to Caramelize Onions

1. Slice the Onions: Peel and thinly slice 4 pounds of yellow onions. Yellow onions offer a sweeter taste when caramelized and give the soup its signature rich flavor.
2. Melt Butter: In a large pot or Dutch oven, melt 3 tablespoons of butter over medium heat. Add the sliced onions and stir to coat them in the butter.
3. Cook the Onions Slowly: Let the onions cook on medium heat for about an hour. Stir occasionally to prevent burning, ensuring that they soften and develop a golden brown color. This slow cooking process enhances their natural sweetness.
4. Increase Heat for Browning: For the last 20 minutes, you can increase the heat to medium-high to deepen the caramelization and achieve a golden, rich color. Stir occasionally to avoid burning.

How to Make French Onion Soup

Build the Flavor: Once the onions are caramelized, add 3 tablespoons of flour to the softened onions and cook for about 2 minutes, stirring constantly. This helps to thicken the soup and build a smooth texture.

Deglaze with Wine: Pour in ½ cup of dry white wine, stirring to deglaze the pot and allow the wine to reduce. This step adds acidity and a complex depth of flavor to the soup.

Add the Stock and Seasoning: Add 6 cups of beef stock (or vegetable stock), 1 teaspoon Worcestershire sauce, 1 bay leaf, and 3 sprigs of thyme (or 1 teaspoon dried thyme). Stir to combine. Bring the soup to a simmer and let it cook for about 10 minutes to infuse the flavors.

Prepare the Baguette Croutons: While the soup simmers, slice the baguette into 1-inch slices. Place the slices on a baking sheet and toast them in the oven at 350°F (175°C) until lightly golden.

Assemble the Soup: Once the soup is done simmering, remove the bay leaf and thyme sprigs. Ladle the hot soup into oven-safe bowls and top each bowl with a toasted baguette slice.

Top with Cheese: Generously sprinkle grated cheese (typically Gruyère or Swiss) over the baguette slices. Place the bowls on a baking sheet and broil for 2-3 minutes until the cheese is melted, bubbly, and slightly browned.

Serve and Enjoy: Serve the French Onion Soup piping hot, garnished with extra fresh thyme or a sprinkle of black pepper, and enjoy the deep, rich flavors.

Storage Instructions

Storing Leftovers: Allow the soup to cool completely before storing it. Place it in an airtight container in the refrigerator, where it will last for up to 3 days.

Freezing: French Onion Soup can be frozen for up to 3 months. To freeze, cool the soup completely and then transfer it into a freezer-safe container. When reheating, be sure to discard any croutons or cheese beforehand. Reheat in a pot over medium heat or in the microwave.

Storing Baguette Croutons: Croutons can be stored separately in an airtight container at room temperature for up to 2 days. Avoid storing them in the soup to prevent them from becoming soggy.

Pro Tips 

Caramelizing Onions: The key to a flavorful French Onion Soup is slow caramelization of the onions. Don’t rush the process; let them cook gently to bring out their natural sweetness.

Use High-Quality Stock: For the richest flavor, opt for beef stock instead of broth. If you prefer a vegetarian version, vegetable stock works well.

Wine Choice: Dry white wine works best to deglaze and balance the richness of the soup. Avoid sweet wines.

Use Gruyère or Swiss Cheese: Gruyère is the classic choice for French Onion Soup, providing both flavor and meltability. You can also use Swiss cheese, but avoid low-fat cheese, as it won’t melt as well.

Thickening the Soup: Adding flour to the caramelized onions helps thicken the broth. If you prefer a thinner soup, you can reduce the flour by half.

Ingredient Substitutes

Yellow Onions: While yellow onions are ideal for their sweetness, you can use white onions or sweet onions if necessary. Just keep in mind the flavor profile will differ slightly.

Beef Stock: For a lighter version, vegetable stock works perfectly in place of beef stock, offering a vegetarian version of the soup.

Wine: If you prefer not to use wine, you can substitute with an additional ½ cup of beef stock or apple cider vinegar for acidity.

Baguette: If you don’t have a baguette, any crusty bread will work, such as ciabatta or sourdough.

FAQS

Can I make French Onion Soup ahead of time?

Yes! You can make the soup a day ahead and store it in the refrigerator. Simply reheat on the stove and assemble with the croutons and cheese just before serving.

Can I freeze French Onion Soup?

Yes, French Onion Soup freezes well. However, do not freeze the croutons or cheese with the soup. Instead, freeze the soup and add fresh croutons and cheese when reheating.

What kind of cheese is best for French Onion Soup?

The traditional cheese for French Onion Soup is Gruyère, but Swiss cheese or even a mixture of Mozzarella and Parmesan can work well if you prefer a different flavor profile.

How do I make French Onion Soup vegetarian?

To make French Onion Soup vegetarian, use vegetable stock instead of beef stock and omit the Worcestershire sauce (or use a vegetarian version).

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