We flipped the script on traditional scalloped potatoes and used sweet potatoes in place of the traditional Yukons or russets and we’re pretty pleased with the results. Evenly sliced potatoes are the key to this recipe’s success so take your time to really slice them ¼-inch thick. If you have a mandolin at home now’s the time to use it. The recipe calls for a 11-by-7-inch baking dish but this will work in a 9-by-13 or other 3-quart baking dish, too. In that case your layers might be a little thinner so just keep an eye on the clock as the gratin may cook a bit faster.