Not quite your mother's pot roast this version has the tender meat and robust gravy of childhood memories, but it is distinguished by a subtle accent of rosemary and orange zest and a creamy sauce made with whole-grain mustard. A puree of wintered-over root vegetables, such as celery root, rutabaga or parsnips, would make a perfect accompaniment for an early spring meal. For a leaner pot roast, choose bottom round or rump roast. Chuck roast is a bit more tender, but fattier.