Sheet-Pan Root Vegetable Gratin

Once the fake-summer tease that is September finally passes and the air starts to smell faintly like wet leaves and sweaters, I, like many people, switch from salad mode to roasted root vegetable mode—preferably the kind that's blanketed in cream and cheese. This sheet-pan root vegetable gratin is the dish I want to live on from the first cool day of fall straight through Thanksgiving. It's a stunner: bubbling, golden, and layered with flavors that taste like the season itself.

This gratin, developed by our colleague Marianne Williams in the Birmingham, Alabama, test kitchen, proves that with the right mix of vegetables, cream, and cheese, along with good use surface area, a simple sheet pan can yield a perfectly browned, evenly cooked result. Instead of baking in a deep casserole dish, which is traditional for gratins, the vegetables are spread out across a rimmed baking sheet. That wider shape means more of the top layer turns brown and crisp, while the vegetables underneath melt into creamy submission. Every serving includes the best of both worlds—the browned, cheesy crust and the silky interior—without having to fight your neighbor for an edge piece. It's also perfect for a crowd or the holiday table since one sheet pan easily serves 8 to 12.

The mix of root vegetables here isn't random. Sweet potatoes bring earthy sweetness; parsnips add a little spice and bite; and golden beets lend both color and a faint minerality. It's just the right combination of sweet, savory, nutty, and just a touch of peppery bite. The onions form the aromatic backbone, cooked gently in butter until soft and golden before being hit with a splash of dry sherry. That quick deglaze adds an acidic punch that keeps the gratin from tasting heavy, even though it's unapologetically rich. The cream soaks up all that flavor, carrying it through every layer of the vegetable.

For cheese, Marianne found that Gruyère and Parmigiano-Reggiano are the winning duo. Gruyère melts into silky strings, while Parm adds sharpness for an extra-savory crust. Fresh thyme and sage thread welcome woodsy flavor through the dish without overpowering it—their aroma is the first to hit you as soon you open the oven door.

What comes out of the oven is something that looks like fall foliage smothered in cheese. It's orange, gold, and pale cream, edged with crisp brown bits and bubbling corners. It's hearty enough to anchor a vegetarian dinner, fancy enough for Thanksgiving, but low-stress enough for a weeknight if you plan ahead. Slice it into neat rectangles or let it rustically spill onto the plate—I guarantee it'll be demolished either way.