This recipe is from Deb Reth, a produce grower who gives the classic vegetable gratin a lift with sweet parsnips and Swiss cheese. Allow ample baking time for the parsnips and potatoes to become tender before browning. Serve this gratin as a vegetarian main dish or as a side for a turkey or ham dinner.
Preheat the oven to 375 degrees and line a baking sheet with parchment paper or foil. Grease a 9-by-13-inch baking dish.
Combine the breadcrumbs with ½ cup of the Swiss cheese and the butter in a bowl and set aside. Whisk the cream, salt and pepper in a measuring cup.
Arrange half of the potatoes in the dish. Pour 1 cup of the cream over them and sprinkle with 1 cup of the Swiss cheese and 1 cup of the parmesan cheese. Arrange half of the parsnips over the cheese, then repeat the layers once more, ending with the last cup of cream. Sprinkle the breadcrumbs evenly over the top.
Cover with foil and place the baking dish on the prepared baking sheet to catch drips. Bake until the vegetables are tender, about 75 minutes. Uncover and bake until golden brown and bubbling, about 15 minutes more.