Clean the mushrooms, peel and finely dice the onion.
Sauté the onion cubes in the melted butter until translucent, add the mushrooms and sauté over medium heat. Add the vegetable broth and let it simmer for about 20 minutes with the pan closed.
In the meantime, cook the pasta until al dente.
Refine the mushroom sauce with the cream and parsley and serve together with the pasta.