Heat 2 tbsp. oil in a large pot over medium-high.
Cook half of mushrooms in a single layer, undisturbed, until edges are brown and starting to crisp, about 3 minutes.
Give mushrooms a toss and 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 and mushrooms and more salt.
Reduce heat to medium-low and return all of the mushrooms to the pot.
Add shallots and cook, stirring often, until shallots are translucent and softened, about 2 minutes.
Meanwhile, cook pasta in a large pot of boiling salted water, stirring occasionally, until very al dente; about 2 minutes less than package directions.
Using tongs, transfer pasta to pot with mushrooms; add cream and 1 cup pasta cooking liquid.
Increase heat to medium, bring to a simmer, and cook, tossing constantly, until pasta is al dente and liquid is slightly thickened, about 3 minutes; remove pot from heat.
Add lemon zest and juice, parsley, butter, ½ oz. Parmesan, and lots of pepper and toss to combine.
Taste and season with more salt, if. needed.
Divide pasta among bowls and top with more Parmesan.
