Flank steak is a fairly popular cut of beef, and for good reason — it's flavorful, inexpensive, and incredibly versatile! Unfortunately I've had my fair share of tough ones over the years; the lean meat almost seems to overcook if you just look at it the wrong way. Thankfully this recipe for balsamic flank steak stuffed with prosciutto and cheese has renewed my faith in the often-too-tough meat.