I’d say the key here is the balsamic, but is it the rosemary, or maybe the garlic, or is the butter? It’s really hard to say which one is the key element to making this simple dish an over the top winner but it doesn’t really matter! What you have here is a dish with about 10-15 minutes prep time 30ish minutes of hands off cook time (for 1.25lbs) and then some serious silence at the table while your family eats in joy.