1 cup cashews
4 Tbsp. (or more) extra-virgin olive oil, divided
6 oz. maitake mushrooms, torn into bite-size pieces
6 oz. shiitake mushrooms, stems removed, torn into bite-size pieces
1 medium leek, white and pale green parts only, halved lengthwise, thinly sliced crosswise
2 medium shallots, finely chopped
2 garlic cloves, thinly sliced
12 oz. spaghetti or other long pasta
2 Tbsp. nutritional yeast
2 Tbsp. finely chopped parsley
Freshly ground black pepper
Looks to be a vegan option for spaghetti
Preheat oven to 350°. Toast cashews on a rimmed baking sheet, tossing halfway through, until golden brown, 7–9 minutes. Let cool.
Heat 2 Tbsp. oil in a large Dutch oven or other heavy pot over medium-high. Arrange half of mushrooms in a single layer in pot and cook, undisturbed, until edges are brown and starting to crisp, about 3 minutes. Give mushrooms a good toss, then continue to cook, tossing occasionally, until all sides are brown and crisp, about 5 minutes more. Using a slotted spoon, transfer mushrooms to a plate; season with salt. Repeat with remaining 2 Tbsp. oil, remaining mushrooms, and more salt.
Reduce heat to medium-low and return all of the mushrooms to same pot. Add leeks, shallots, and garlic and cook, stirring often and adding another 1 Tbsp. oil if pan looks dry, until leeks and shallots are translucent and softened, about 4 minutes. Remove from heat.
Meanwhile, cook pasta in a large pot of boiling salted water, stirring occasionally, until very al dente, about 2 minutes less than package directions (the pasta will finish cooking in the pan). Drain pasta, reserving ¾ cup pasta cooking liquid.
Blend cashews, nutritional yeast, and pasta cooking liquid in a blender until very creamy. Set cashew cream aside.
Return drained pasta to pot with mushroom mixture and add reserved cashew cream. Place over medium heat and cook, stirring well to coat, until pasta is al dente, about 3 minutes. Remove from heat. Add parsley and squeeze in juice from lemon half. Toss well to incorporate.
Divide pasta evenly among shallow bowls or plates and top with several grinds of pepper.