½ cup Parmesan, finely grated, plus more for serving
black pepper, freshly ground
1Heat 2 Tbsp olive oil in a large pot over medium-high heat. Cook half of mushrooms in a single, undisturbed layer until edges brown and start to crisp, about 3 minutes. Continue cooking mushrooms, tossing occasionally, until all sides are brown and crisp, about 5 minutes more. Using a slotted spoon, transfer mushrooms to a plate and season with salt. Repeat with remaining oil, mushrooms, and more salt.
2Reduce heat to medium-low and return all mushrooms to the pot. Add shallots and cook, stirring often, until shallots are translucent and softened, about 2 minutes.
3Meanwhile, cook pasta in a large pot of boiling salted water, stirring occasionally, until very al dente, about 2 minutes less than package directions.
4Using tongs, transfer pasta to pot with mushrooms. Add cream and 1 cup pasta cooking liquid, increasing heat to medium until mixture is simmering. Continue to cook, tossing constantly, until pasta is al dente and liquid is slightly thickened, about 3 minutes.
5Remove pot from heat. Add parsley, butter, Parmesan, and a generous amount of pepper, tossing to combine. Taste and season with more salt if needed.
6Divide pasta among bowls and top with more parmesan and parsley, if desired.