Heat oven to 425 degrees F. Rub beef with oil; sprinkle with pepper. Place beef on rack in shallow roasting pan, or place diagonally in 15x10x1-inch pan. Insert ovenproof meat thermometer so tip is in center of thickest part of beef.

Bake uncovered 30 to 45 minutes or until thermometer reads 135 degrees F. Cover beef loosely with tent of foil and let stand 15 to 20 minutes until thermometer reads 145 degrees F (medium-rare doneness). (Temperature will continue to rise about 10 degrees F and beef will be easier to carve.)

Meanwhile, in 12-inch nonstick skillet, melt butter over medium heat. Cook onion, garlic and mushrooms in butter 8 to 10 minutes, stirring occasionally, until mushrooms are completely tender and beginning to brown. Stir in sherry. In small bowl, mix cornstarch and water; stir cornstarch mixture into mushroom mixture. Stir in thyme, pepper and beef consomme; cook and stir about 2 minutes or until slightly thickened and bubbly. Stir in mustard and tomato paste until well blended. Heat just until hot. Spoon sauce over sliced beef.

High Altitude (3500-6500 ft): In step 3, increase second cook time to 4 minutes.