Salt and Pepper the filet.
In a skillet, melt 1/3 of the butter with the oil and sauté the filet over high heat for four minutes on each side.
For medium rare, sauté them for one minute on each side. Remove meat from skillet, set aside and keep warm.
In the same skillet add 1/3 more butter and sauté the mushrooms over high heat for three minutes. Still over high heat; add the Madeira (a splash of cognac will add a nice flavor as well), then add the cream and cook for two minutes more.
Stir in the remaining butter while cooking for one minute more. The sauce should be silky.
Pour the mushroom sauce over the meat, serve hot. Any vegetable is a good garnish for this beef.
