French onion soup is a classic well suited for fall. The dark, rich broth and cheese-encrusted top are perfect for fending off a chilly evening.
For our version, we added a few more members of the onion family (leeks and shallots), a handful of herbs, as well as the earthiness of mushrooms. If you'd like to keep it vegetarian, you can swap out the beef and chicken broths for vegetable broth.
ONION AND MUSHROOM SOUP
Start to finish: 1 hour
2 ounce-package dried porcini or similar mushrooms
1 cup boiling water
5 tablespoons butter, divided
3 large sweet onions, thinly sliced
1/4 cup white wine
2 leeks, white parts only, cleaned and sliced
2 shallots, chopped
2 cloves garlic, minced
2 tablespoons chopped fresh thyme
2 tablespoons chopped fresh rosemary
3 tablespoons all-purpose flour
2 cups chicken broth
2 cups beef broth
Salt and ground black pepper, to taste
4 slices stale crusty bread
4 slices fontina cheese
Chopped fresh chives, for garnish
Cut or break the dried mushrooms into small pieces and place in heat-safe bowl. Pour the boiling water over the mushroom pieces and set aside.
In a large saucepan over medium heat, melt 3 tablespoons of the butter. Add the onions and cook slowly until well-browned, stirring regularly, about 15 to 20 minutes. If the onions begin to get too browned, add a couple teaspoons of water. When the onions are browned and caramelized, add the wine and stir to deglaze the pan. Add the leeks, shallots, garlic, thyme, rosemary and remaining 2 tablespoons of butter.
Increase the heat to medium-high and cook until the leeks are tender, about 6 to 8 minutes. Add the flour and stir to coat everything. Pour in the chicken and beef broths, then stir well and bring to a boil. Add the steeped mushrooms (including the liquid), then reduce heat to simmer for 10 minutes. Season with salt and pepper.
Heat the broiler.
Ladle the soup into four oven-safe crocks. Top each with a slice of the stale bread, then a slice of the cheese. Arrange the crocks on a rimmed baking sheet, then place under the broiler and cook until the cheese is melted and begins to brown, 1 to 2 minutes. Serve topped with fresh chives.