Gratin de Topinambours et Pommes de Terre

One year we planted a few jerusalem artichokes in the garden and we’ve had them ever since, for they are persistent and prolific plants. At La Varenne in Paris, the chefs are adept at turning a weekly crateful of roots into delicacies and this recipe, a version of potato ‘gratin dauphinois’ is one of their best inventions. Turnips can be substituted for the artichokes. A rich gratin like this is often served with roast or grilled beef.