• You will need about 8 - 10, 10-inch pieces of kitchen twine.
• ***If your butcher has already butterflied the flank steak for you, skip to step 3 after preheating oven.
• Preheat oven to 450°F.
• How to butterfly flank steak: Using a sharp knife, carefully slice the the flank steak lengthwise into two pieces, but do not cut all the way through. With a meat tenderizer or rolling pin, pound the steaks until they are as evenly thin as possible, no more than about 1/2-inch thick. Sprinkle with salt and pepper on both sides.
• In a small bowl, combine the cheese, rosemary, parsley, thyme, and garlic, set aside.
• Layer the thinly sliced prosciutto over the steak, leaving a 1 inch border all around.
• Scatter the herb and cheese mixture over the prosciutto. 
• From the short side, start to roll the steak up so that the grain of the meat runs the length of the roll. Tie the steak close with the twine about every 2 inches. 
• In a small mixing bowl, whisk together the balsamic vinegar, olive oil and garlic powder together, place in a 9x13 casserole dish. Place the stuffed flank steak into the dish, rolling it in the balsamic mixture until it is well covered all over, make sure the stuffed flank steak is seam side down before cooking.
• Bake uncovered in the 450°F preheated oven, and cook for 35 - 45 minutes, for medium rare. Remove from oven, cover with foil and allow to rest for no less than 15 minutes or up to 30 minutes before slicing.
• Once the meat has been allowed to rest, cut the twine to remove, and slice into flank steak pinwheels, , about 1 inch thick, and serve spiral side up. 

Enjoy!