French Onion Soup with Mushrooms, Extra Herbs & Cheesy Croissant Topping
A warm, savory soup that blends caramelized onions and mushrooms with herbs, topped with gooey, melty cheese and flaky croissant.
Ingredients
For the Soup Base
- 4 large yellow onions, thinly sliced
- 8 oz mushrooms, sliced (cremini or button)
- 3 tbsp butter
- 1 tbsp olive oil
- 2 cloves garlic, minced
- 1 tsp dried thyme or 1 tbsp fresh thyme leaves
- 1 leaf bay leaf
- 1/2 cup dry white wine or sherry (optional)
- 6 cups beef or vegetable broth Use vegetable broth for a vegetarian option.
- to taste salt and black pepper
For the Topping
- 2 large croissants, torn into pieces
- 1 1/2 cups grated Gruyère or Swiss cheese Can also use Emmental or fontina as alternatives.
Instructions
Preparation
- Heat butter and oil in a large pot over medium-low heat.
- Add onions and cook slowly, stirring often, until deep golden brown, about 35–45 minutes.
Cooking
- Add mushrooms and cook for 5–7 minutes until soft.
- Stir in garlic, thyme, and bay leaf for 1 minute.
- Pour in wine and scrape brown bits from the pot. Let wine reduce by half, about 2–3 minutes.
- Add broth, bring to a simmer, and cook for 15–20 minutes. Season with salt and pepper. Remove bay leaf.
Broiling
- Preheat broiler. Divide soup into oven-safe bowls.
- Top each bowl with croissant pieces and a generous layer of grated cheese.
- Broil for 2–4 minutes until cheese is melted and golden, watching closely to avoid burning.
Notes
Cool the soup before storing. Store broth and croissant pieces separately for best texture. Freeze broth (no croissant) for up to 3 months.