How to make a creamy mushroom sauce. Chop an onion, four cloves of garlic and 250 grams of mushrooms into thin slices. Saute the onion and garlic in a frying pan with a little olive oil. Add the mushrooms. When the mushrooms are cooked, add 250 grams of cream cheese and 250 milliliters of milk. Stir until it binds. Season with salt and pepper to taste and then, add a pinch of fresh rosemary. Serve your sauce with a freshly baked rigatoni!