Heat 2 tablespoons butter in a skillet over medium low heat; add mushrooms and cook for about 4 minutes, or until lightly browned. Add the scallions and cook for 1 to 2 minutes longer. Sprinkle with 1/4 teaspoon of pepper; set aside.
In a large skillet, heat 2 tablespoons butter and 1 tablespoon of olive oil over medium heat until the butter begins to foam. When foaming subsides slightly, add the tenderloin medallions. Saute on both sides until browned and medium rare. Remove the medallion to a platter and keep wram. To the skillet the beef was cooked in add the red wine and beef broth. Boil, scraping up the browned bits, reducing the liquid by about half. Combine cornstarch with the heavy cream, blending well. Whisk the cream mixture into skillet and simmer for 1 minute. Add mushrooms and scallions to the cream sauce and simmer for 1 minute longer. Add salt, to taste. Add the beef medallions and juices from the platter to the cream sauce, coating beef with sauce. Cover and heat for 2 minutes on low. Add the remaining 1 tablespoon of butter, blending well.
Garnish with fresh chopped parsley and serve with baked or mashed potatoes.
Serves 4 to 6
Calories per serving (based on 6 servings): 547
Fat per serving (based on 6 servings): 37.1