Ingredients
Soup Base
- 3 tablespoons butter
- 2 tablespoons olive oil
- 4 large yellow onions, thinly sliced
- 1 teaspoon sugar (optional, helps caramelization)
- 2 cloves garlic, minced
- ½ cup dry white wine (optional)
- 6 cups beef broth
- 1 teaspoon fresh thyme (or ½ teaspoon dried thyme)
- 1 bay leaf
- Salt and black pepper, to taste
Topping
- 1 baguette, sliced and toasted
- 1½ cups shredded Gruyère cheese
Instructions
- Caramelize Onions: Heat butter and olive oil in a large pot over medium heat. Add the thinly sliced onions and cook, stirring occasionally, for 30 to 40 minutes until the onions are deeply golden and caramelized, developing rich sweetness and flavor.
- Add Sugar and Garlic: Sprinkle in the optional sugar to enhance caramelization. Add the minced garlic and cook for an additional 30 seconds, releasing its aroma without burning.
- Deglaze with Wine: Pour in the dry white wine to deglaze the pot, scraping up any browned bits stuck to the bottom for depth of flavor. Let it simmer for 2 to 3 minutes until the alcohol cooks off and the liquid reduces slightly.
- Add Broth and Herbs: Pour in the beef broth, add fresh thyme and a bay leaf. Bring the soup to a gentle simmer and cook for 20 minutes to marry the flavors and develop richness.
- Season and Remove Bay Leaf: Season the soup with salt and black pepper according to taste. Remove and discard the bay leaf before serving.
- Prepare Bowl and Broil: Preheat your oven broiler. Ladle the hot soup into oven-safe bowls, top each serving with toasted baguette slices, and generously sprinkle shredded Gruyère cheese on top.
- Broil Soup: Place the bowls under the preheated broiler for 2 to 3 minutes until the cheese melts, bubbles, and develops a golden crust. Serve immediately while hot and bubbly.
Notes
- Take your time caramelizing the onions for the best rich and sweet flavor.
- Use beef broth for the classic savory flavor, or substitute with vegetable broth to make a vegetarian version.
- Gruyère cheese can be replaced with Swiss or provolone if preferred or unavailable.
- Store leftover soup without bread and cheese in an airtight container in the refrigerator for up to 4 days.
- Prep Time: 15 minutes
- Cook Time: 1 hour
- Category: Soup
- Method: Simmering
- Cuisine: French
- Diet: Vegetarian
