Grate the Parmesan cheese.
Remove the base of the mushroom stems, wash them, and then slice them.
In a large pot, heat 4 liters of water with 28 grams of salt.
When the water boils, add the pasta at once and cook for 9 minutes.
After 8 minutes, reserve 100 ml (3.4 oz) of the pasta cooking water.
In a large pan or skillet, sauté the mushrooms in butter with a little salt over very high heat for 5 minutes.
Add the 100 ml of reserved pasta cooking water, the crème fraîche, and 2/3 of the grated Parmesan. Mix well.
Drain the pasta.
Add the pasta to the pan, coat them with the sauce, and continue cooking for 2 minutes.
Generously pepper the dish.
Divide the pasta into shallow bowls.
Garnish with grated Parmesan and chopped basil.