Ingredients
Scale
For the Soup:
- 5 large yellow onions, thinly sliced
- 3 tablespoons unsalted butter
- 1 tablespoon olive oil
- 1 teaspoon sugar
- 2 garlic cloves, minced
- 2 tablespoons balsamic vinegar
- 6 cups beef broth (or vegetable broth for a vegetarian version)
- 2 bay leaves
- 1 teaspoon dried thyme
- Salt and pepper, to taste
For the Topping:
- 1 French baguette, sliced
- 1 ½ cups shredded Gruyère cheese (or Swiss/provolone as substitutes)
Instructions
1. Caramelize the Onions:
- In a large pot or Dutch oven, melt the butter with olive oil over medium heat.
- Add the sliced onions and stir to coat evenly.
- Cook for 10 minutes, then sprinkle with sugar and a pinch of salt.
- Reduce the heat to low and cook for 35-40 minutes, stirring occasionally, until onions are golden brown and caramelized.
2. Build the Flavor:
- Stir in minced garlic and cook for 1 minute.
- Add balsamic vinegar, scraping up any browned bits from the bottom of the pot. Simmer for 2-3 minutes.
3. Simmer the Soup:
- Pour in the beef broth, and add bay leaves and thyme.
- Bring to a gentle simmer and cook for 20-25 minutes. Adjust seasoning with salt and pepper to taste.
- Remove and discard the bay leaves before serving.
4. Prepare the Topping:
- Preheat the oven to 400°F (200°C). Arrange baguette slices on a baking sheet and toast for 5-7 minutes until golden and crisp.
5. Final Assembly:
- Ladle the soup into oven-safe bowls.
- Place a toasted baguette slice on top of each bowl and sprinkle generously with shredded Gruyère cheese.
- Place the bowls on a baking sheet and broil for 2-3 minutes, or until the cheese is melted and bubbly.
Notes
- Caramelization Takes Time: Slow cooking the onions is essential for their sweet, rich flavor. Be patient and stir occasionally.
- Use High-Quality Ingredients: Opt for fresh onions, authentic Gruyère cheese, and good-quality broth for the best results.
- Oven-Safe Bowls: Ensure your bowls can withstand broiling to avoid cracking.
- Adjust Seasonings: Taste the soup during simmering and adjust salt and pepper as needed.
- Serve Fresh: Assemble the topping just before serving for the perfect texture.
- Prep Time: 10minutes
- Cook Time: 1 hour 10 minutes