Oh, we know the myth. The best hamburgers are made from ground chuck, because the meat has more fat in it. The fat then prevents the burger from shrinking into a McDonald's-esque disk while cooking. Well, baloney. At the downtown location of Morton's, the hamburger is a full eight ounces of lean ground sirloin. Hard to feel guilty eating that. And it's just about the juiciest thing we've encountered outside the Chris Paciello story. The single drawback? The burger is served only during the noontime meal. Still, order with a side of lyonnaise taters, and that's what we call a power lunch.