Bring a large pot of salted water to a boil and cook the pasta until al dente. Reserve a cup of the cooking water before draining.
While the pasta cooks, melt the butter in a large pan over medium heat. Add the mushrooms and cook until golden and tender.
Stir in the garlic and cook for another minute until fragrant.
Pour in the cream and let it simmer for 3 to 4 minutes. Stir in the Parmesan until melted into the sauce.
Add the cooked pasta to the pan and toss to coat, adding a splash of the reserved pasta water if needed to loosen the sauce.
Season with salt and pepper. Serve hot, sprinkled with parsley if you like.