One-Pot French Onion Soup With Porcini Mushrooms

Step 1

Bring 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 2

Melt 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 3

Add fennel and leeks, season again, and cook, covered, stirring occasionally, 15 minutes.

Step 4

Remove 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 5

Scoop 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 6

Meanwhile, 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.