Clean the mushrooms and cut them into thin slices. Chop onion and garlic.
Heat the olive oil in a large skillet. Saute the onion and the garlic for 1-2 minutes and then add the mushrooms. On fairly high heat saute them until nearly all of their liquid has evaporated. Add the white wine and continue cooking on high heat for some minutes.
Reduce the heat and simmer gently until sauce has thickened. Now add the cream and season with salt and pepper to taste (you might also like to add some Italian herbs).
If you like add the parmesan cheese to get an even creamier sauce.