Set oven control to broil. Line 15x10-inch pan with sides with foil. Rub both sides of each steak with cut side of garlic. Sprinkle each side with pepper; place steaks in pan.
Broil 4 to 6 inches from heat 12 to 16 minutes, turning once, until desired doneness.
Meanwhile, in 7-inch nonstick skillet, melt butter over medium heat. Add mushrooms and shallots; cook 4 to 6 minutes, stirring frequently, until shallots are tender and mushrooms begin to brown. Add wine; cook 1 minute, stirring occasionally.
In small bowl, mix broth and cornstarch until smooth. Gradually stir into mushroom mixture, cooking and stirring until bubbly and thickened. Serve sauce over steaks.