2 lbs mixed wild mushrooms (such as shiitake, trumpet, oyster, and chanterelle), coarsely chopped
freshly ground black pepper
1 cup parmesan cheese, grated, plus more for serving
1 cup toasted walnuts, chopped
½ cup chopped fresh parsley
Bring a large pot of salted water to a boil. Cook the fettuccine until al dente according to package directions; you want some bite left so it can finish cooking with the sauce. Drain the pasta, reserving 1 cup of the cooking water, and toss pasta with 1 tbsp olive oil. Set aside.
Melt the butter in a large skillet over medium-low heat. When the butter begins to foam, stir with a wooden spoon to encourage evaporation and help the solids brown evenly. Continue stirring until the butter smells nutty and the solids turn a rich golden brown, 3-5 minutes. Add shallot and garlic and cook until fragrant, about a minute. Add 2 tablespoons of olive oil, stir to mix, then pour half of the mixture into a bowl and set aside.
Raise the heat to medium-high and add half of the mushrooms, to prevent overcrowding and get really crispy edges. Season with salt and pepper and toss to coat. Cook, stirring occasionally until mushrooms have released their water and they are brown and crispy, about 15 minutes. Transfer to a large bowl and repeat with remaining butter mixture and mushrooms.
Add cooked pasta, parmesan and the cooking water to the skillet and toss to combine. Cook over medium-high heat until the water reduces to a thick, shiny sauce, about 5 minutes. Add cooked mushrooms, walnuts and parsley and toss to combine. Season with salt and pepper. Serve with extra parmesan.