Grilled Beef Tenderloin with Marsala-Mushroom Sauce

4 Servings

4 tablespoons (V2 stick) butter
1 cup chopped leek (white and pale green parts only)
4 teaspoons minced garlic
4 cups sliced mixed fresh wild mushrooms (such as oyster; stemmed portobello and stemmed shittake)
2/3 cup dry Marsala
2/3 cup beef stock or canned broth

4 8-ounce beef tenderloin steaks
Olive oil

Melt 2 tablespoons butter in heavy large skillet over medium-low heat. Add leek and garlic and saute' until almost tender about 5 minutes. Increase heat to medium- high. Add mushrooms and saute' until golden brown, about 6 minutes. Add Marsala and stock and boil until liquid is reduced by half about 4 minutes. Strain sauce, reserving mushrooms. (Can be prepared 1 day ahead. Cover strained sauce and mushrooms separately and chill.)
Prepare barbecue (medium-high heat) or preheat broiler. Brush steaks with olive oil. Sprinkle with salt and pepper. Grill to desired doneness, about 4 minutes per side for medium-rare. Transfer to platter and tent with foil.

Bring sauce to simmer in heavy large skillet. Remove skillet from heat. Gradually whisk in remaining 2 tablespoons butter. Add reserved mushrooms and stir over low heat until mushrooms are heated through, about 2 minutes. Season to taste with salt and pepper.

Place steaks on plates. Spoon sauce and mushrooms over and serve.