Celeriac more often serves as a cooked vegetable than branch celery (two parts of celeriac parboiled with one part of potatoes, well drained, puréed, and generously buttered, is a splendid accompaniment to roast lamb, beef, or venison—mysterious and exquisitely flavored white purées may be conceived by a judicious addition of onions and garlic cloves, parboiled with them, and turnips, parboiled apart and stewed in butter before being combined into the purée . . .), but hearts of the latter, braised, are among the more sumptuous of roast garnishes. The syrupy braising juices may, removed from the heat, be bound by whisking in butter or, once braised, the hearts may be transformed into a gratin with a sprinkling of Parmesan and some 20 minutes in a hot oven.