Ingredients :

• Brown button mushrooms (cremini) — It’s essential to get brown, not white. They have a more earthy flavor and hold up better during slow cooking. Classic white ones become watery and tasteless after three hours. Allow 400g for four people.
• Full-fat crème fraîche — This is what makes the velvety sauce. Low-fat cream will split under prolonged heat and yield a grainy sauce — avoid that. If you want to lighten it slightly, go half full-fat cream, half whole milk, but no less.
• Short pasta (penne or rigatoni) — Tubes with ridges catch the sauce. The short shape also makes it easier to serve in a bowl. Spaghetti or linguine are a nightmare to portion when everyone is around the table getting hungry.
• Block Parmesan — Grate it yourself if you can. Bagged parmesan contains anti-caking starch that creates lumps in a hot sauce. A real piece grated by hand makes a real difference in the finish.