French Onion Soup with Truffle Oil

🕒 Prep: 10 min
🔥 Cook: 1 hour
🍽 Serves: 6
★★★★★
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French Onion Soup with Truffle Oil is a luxurious twist on a classic favorite. This recipe combines the rich, comforting flavors of caramelized onions and beef broth with a hint of elegance from truffle oil. Perfect for a cozy night in or a special occasion, it’s a dish that warms both the body and the soul.

Ingredients for French Onion Soup with Truffle Oil

Yellow onions are the star here, providing the sweet, caramelized base. Unsalted butter and olive oil help achieve that deep golden color while adding richness. A touch of salt and sugar helps to balance and enhance the natural sweetness of the onions. All-purpose flour thickens the soup slightly, giving it body. Beef broth forms the flavorful foundation, while dry white wine adds depth and complexity. Bay leaf and fresh thyme infuse the soup with aromatic notes. The blend of Gruyère and Mozzarella cheese melts beautifully, providing a cheesy, golden topping. Finally, a drizzle of truffle oil adds a luxurious finish.

Tips & Tricks

  • Use a mandoline to slice onions evenly for consistent cooking.
  • Low and slow is key for caramelizing onions; don't rush this step.
  • For an even richer flavor, use homemade beef broth if available.
  • Make sure your oven-safe bowls can handle the broiler's heat.

Serving Suggestions

This French Onion Soup pairs beautifully with a simple green salad dressed with a tangy vinaigrette. For a heartier meal, serve alongside a charcuterie board featuring cured meats and pickles to balance the soup's richness.

Frequently Asked Questions

Can I use a different type of onion?
Yes, but yellow onions provide the best balance of sweetness and flavor when caramelized.
What can I substitute for white wine?
You can use additional beef broth or a splash of apple cider vinegar for acidity.
Is truffle oil essential?
No, but it adds a unique flavor. If unavailable, consider using a drizzle of good-quality olive oil instead.

French Onion Soup with Truffle Oil Recipe Walkthrough

Start by melting the butter with olive oil in a large pot over medium heat. Toss in the thinly sliced onions, along with salt and sugar. Cook these slowly, stirring often, until they are deeply caramelized and golden brown, which should take about 25 minutes. This step is all about patience as the onions transform into a sweet, jammy base.

Once your onions are perfectly caramelized, sprinkle the flour over them, stirring for a minute or two. This helps the flour cook out its raw taste and blend with the onions.

Next, gradually pour in the beef broth and white wine, stirring to combine. Toss in the bay leaf and thyme. Bring the mixture to a simmer and let it cook for about 30 minutes, stirring occasionally. This allows the flavors to meld beautifully.

Season your soup with salt and pepper to taste, then remove and discard the bay leaf. Preheat your broiler while you prepare the bread.

Arrange the sliced baguette on a baking sheet and toast them in the oven until they're golden and crisp. This will be the base for your cheesy topping.

Ladle the hot soup into oven-safe bowls, topping each with toasted baguette slices. Generously sprinkle with Gruyère and Mozzarella. Place the bowls on a baking sheet and broil in the oven until the cheese is melted and bubbly, usually 3-5 minutes.

Finish each bowl with a drizzle of truffle oil just before serving for that final touch of luxury.

Why You'll Love This Recipe

  • Elevated flavor profile with a touch of truffle oil.
  • Simple ingredients that transform into a gourmet experience.
  • Perfect for impressing guests without spending hours in the kitchen.
  • The combination of Gruyère and Mozzarella creates an irresistible cheesy crust.

Ingredients

2 lbs yellow onions, thinly sliced
4 tbsp unsalted butter
1 tbsp olive oil
1 tsp salt
1/2 tsp sugar
3 tbsp all-purpose flour
8 cups beef broth
1/2 cup dry white wine
1 bay leaf
1 tsp fresh thyme leaves
3/4 cup Gruyère cheese, grated
1/2 cup Mozzarella cheese, grated
1 tbsp truffle oil
1 baguette, sliced into 1-inch rounds
Salt and pepper to taste

Step-by-step Instructions

1. In a large pot, melt butter with olive oil over medium heat. Add sliced onions, salt, and sugar. Cook, stirring often, for about 25 minutes until onions are deeply caramelized and golden brown.
2. Sprinkle flour over the onions and stir for 1-2 minutes.
3. Gradually add beef broth and white wine, stirring to combine. Add bay leaf and thyme. Bring to a simmer and cook for about 30 minutes, stirring occasionally.
4. Season with salt and pepper to taste. Remove bay leaf and discard.
5. Preheat the broiler. Place baguette slices on a baking sheet and toast in the oven until golden.
6. Ladle soup into oven-safe bowls. Top each with toasted baguette slices, sprinkle with Gruyère and Mozzarella cheeses.
7. Place bowls on a baking sheet, broil in the oven until cheese is melted and bubbly, about 3-5 minutes.
8. Drizzle with truffle oil before serving.

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