1. Mix together balsamic vinegar, garlic and 1/3 cup olive oil to create marinade.
2. Lay the steak on a work surface, with a short edge facing you. Press one hand flat on the meat to keep it still. Using a long, sharp knife, make a horizontal cut in a long side of the steak to within 1/2 inch of the opposite edge. Marinate steak in a refrigerator for 4 hours - 24 hours. (In plastic bag or glass baking dish covered)
3. Preheat the oven to 350°F. In a large bowl, combine the bread crumbs, cheese, and 2 tablespoons of olive oil.
4. Open the flank steak like a book.
5. Cover the cut side of the steak with the prosciutto slices, then top with a layer of basil leaves. Spread the bread crumb mixture on top. Starting with the side facing you, tightly roll up the steak around the filling. Using kitchen string, tie the roll in 4 places, or secure with toothpicks that have been soaked in water.
6. Drizzle with remaining olive oil. Sprinkle with salt and pepper.
7. Place steak in an ovenproof pan. Sear flank steak on all sides over medium heat to create a char. Then place in oven and roast, for 20 to 30 minutes, or until an internal temperature reaches 125°F for medium rare.
8. Transfer the rolled steak to a carving board, cover loosely with foil and let rest for 10 minutes. Discard the strings or toothpicks and slice the steak into 1/2 inch thick pieces and enjoy!