Sprinkle beef with salt and pepper. Grill beef, covered, over medium heat or broil 4 in. from the heat for 4-6 minutes on each side or until meat reaches desired doneness (for medium-rare, a thermometer should read 135°; medium, 140°; medium-well, 145°). Let stand for 5 minutes. Thinly slice across the grain., Meanwhile, in a small bowl, combine the oil, garlic and basil; brush lightly over baguette slices. Place on baking sheets. Bake at 400° for 5 minutes. Top with mushrooms and mozzarella cheese. Bake 2-3 minutes longer or until cheese is melted., Top with sliced steak, Parmesan cheese and chives. Serve immediately.