Weighing the meat on a kitchen scale is the most accurate way to portion it. If you don’t own a scale, do your best to divide the meat evenly into quarters. Eighty percent lean ground chuck is our favorite for flavor, but 85 percent lean works, too. If you start with a chuck roast or steak, ask the butcher to grind it twice and expect some weight loss - 2 to 3 percent in our experience - to the grinder. Toasting the buns is an easy extra flourish; just split them open and lay the halves cut-side down on the grill rack for the last 45 to 60 seconds of the hamburgers’ cooking time.
