This wonderful recipe for potatoes au gratin involves layering thinly sliced potatoes with heavy cream and grated cheese in a baking dish, and then baking until the cream thickens and blankets the potatoes in a rich, creamy sauce. I’d say the dish is worthy of a special occasion — it is! — but the truth is that eating it is a special occasion unto itself. The only consideration to keep in mind is that the dish is best assembled right before baking. Once potatoes are peeled and sliced, they discolor quickly. Similarly, it cannot be baked ahead of time, as the cream tends to separate when reheated. I hope this doesn’t discourage you from trying the recipe, as it is truly delicious and worth the effort.