One-Pot French Onion Soup With Porcini Mushrooms
This version of the classic French soup simmers and bakes in a Dutch oven, while the toast broils right on top. Dried porcini mushrooms, fresh fennel and leeks provide deep umami flavor. Unless you have homemade beef stock on hand, go with a good chicken stock rather than boxed beef stock, which tastes mostly of salt. You could opt for vegetable stock for a vegetarian version, but skip the demi-glace, in that case. The preparation of this soup is time-consuming, but the flavor is well worth the effort. You can make the soup through Step 5 up to two days ahead of time. When ready to serve, reheat on the stove then continue with the final baking step for a hearty communal feast.
- Serves: 6 persons
- 1ounce dried porcini mushrooms
- 4tablespoons unsalted butter
- 2tablespoons olive oil
- 4large yellow onions (about 3 1/2 pounds), halved and cut into 1/4-inch slices
- Kosher salt and black pepper
- 1large fennel bulb, trimmed, halved lengthwise and thinly sliced crosswise
- 1large or 2 small leeks, trimmed, halved lengthwise and thinly sliced crosswise
- 2tablespoons all-purpose flour
- 1cup dry white wine
- 2large fresh thyme sprigs
- 1fresh or dried bay leaf
- 2quarts homemade beef stock or store-bought chicken stock
- 1to 2 tablespoons veal, beef or chicken demi-glace or stock concentrate (optional)
- 6(3/4-inch-thick) slices sourdough, peasant or other good-quality bread (about 8 ounces), toasted
- 1 ½cups grated Gruyère (about 4 ounces)
- ¾cup grated Parmesan (about 2 ounces)
Step 1Bring a small saucepan with about 2 1/2 cups water to a boil over high and place mushrooms in 2-cup glass measuring cup. Pour boiling water over the mushrooms to fill the cup (a little less than 2 cups) and set aside.
Step 2Melt butter in a large Dutch oven over medium heat. Stir in oil and onions, cover and cook, stirring occasionally, until wilted, about 15 minutes. Turn heat up to medium-high, season with salt and pepper and continue cooking, covered, stirring occasionally, 15 minutes.
Step 3Add fennel and leeks, season again, and cook, covered, stirring occasionally, 15 minutes.
Step 4Remove lid, increase heat to high and cook, stirring frequently, until the vegetables are deeply browned, about 5 minutes. Lower the heat if the buildup on the bottom of the pot threatens to burn. Sprinkle with flour and cook, stirring, 1 to 2 minutes.
Step 5Scoop the mushrooms out of their liquid, reserving liquid and chop mushrooms finely. Add chopped mushrooms, wine, thyme sprigs and bay leaf to the pot. Cook, scraping the bottom of the pot with a wooden spoon, until wine is mostly evaporated, 2 to 3 minutes. Add reserved mushroom liquid to the pot, pouring the liquid slowly and discarding the last few drops of liquid, which may contain grit. Pour in the stock and demi-glace, if using, and bring to a boil, scraping the bottom of the pot to loosen any residue. Reduce to a simmer, and cook uncovered until flavors meld, about 30 minutes. Discard thyme sprigs and bay leaf. Season to taste with salt and pepper.
Step 6Meanwhile, heat oven to 375 degrees. Fit the toasted bread on the surface of the soup in an even layer, breaking them up as needed to cover the surface. Sprinkle with the Gruyère and Parmesan. Set the Dutch oven on a baking sheet and bake in the middle of the oven until the cheese is bubbling, 15 to 20 minutes. Heat oven to broil and continue cooking until cheese is melted and golden brown, 1 to 2 minutes. Serve immediately.