Cheesy Root Vegetable Gratin
I fell in love with this Cheesy Root Vegetable Gratin the first time I made it for a chilly November potluck. I remember carrying the dish through a drizzle, the kitchen smelling of garlic and thyme, and hearing a chorus of surprised “oohs” when I uncovered the browned, bubbling top. There’s something quietly celebratory about a dish that turns humble roots — sweet potatoes, parsnips and beets — into an elegant, cheesy centerpiece. This gratin is creamy, layered with nutty Parmesan and gooey Gruyère, and easy enough for a weeknight but pretty enough for holiday company. 
In this post I’ll walk you through every step to make a perfectly tender, golden Cheesy Root Vegetable Gratin. You’ll learn how to prep the vegetables for even baking, time the oven so the top browns without drying out the interior, and a few smart swaps if you don’t have all the cheeses on hand. Ready to turn root vegetables into something unforgettable? Let’s do it.
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Why this Cheesy Root Vegetable Gratin works
This gratin balances three things: texture, fat, and flavor. Thinly sliced vegetables cook through quickly and stack neatly so each bite has a little of everything. Heavy cream and a splash of extra cream in the baking dish provide the lush, silky sauce while grated Parmesan melts into the layers offering savory saltiness. A final shower of shredded Gruyère gives that signature golden, bubbling finish. Fresh thyme ties the earthiness of the beets and parsnips to the sweet potato’s natural sugars.
Prep tip: use a mandoline to get thin, even slices — it’s the single best way to ensure consistent cook time.
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Ingredients
– 1 tablespoon unsalted butter, softened (for greasing the dish)
– 1–2 long sweet potatoes (about 2 inches thick), peeled
– 3–4 large parsnips, ends trimmed and peeled
– 3–5 small beets, peeled
– 14 tablespoons (7/8 cup) heavy cream, divided (whole milk will work but won’t be as rich)
– 4 ounces grated Parmesan, divided
– 1 tablespoon fresh minced thyme, divided (plus extra for garnish)
– 1 garlic clove, minced
– 1 ounce shredded Gruyère
– Salt and freshly ground black pepper, to taste
Makes about 6 servings as a side.
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Equipment you’ll need
– Mandoline or very sharp knife
– 3-quart (oval recommended) baking dish
– Mixing bowls for each vegetable
– Aluminum foil
– Grater for Parmesan and Gruyère (if not pre-shredded)
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Step-by-step instructions
1. Preheat the oven to 400°F (205°C) and grease a 3-quart baking dish with the softened butter. Make sure the butter reaches the sides so the cheese won’t stick later.
2. Slice the sweet potatoes, parsnips and beets into very thin rounds (about 1/16–1/8 inch). A mandoline makes this fast and consistent; if you’re using a knife, take your time and keep the slices even. Transfer each vegetable to its own bowl.
3. Divide the cream among the bowls: pour 4 tablespoons of cream over the sweet potatoes and 4 tablespoons over the parsnips, and 2 tablespoons over the beets. This partial pre-coating helps each vegetable absorb richness and salt.
4. To each bowl, add 1/2 ounce (about 1/2 cup grated) Parmesan and 1 teaspoon minced thyme. Season each bowl generously with salt and pepper. Toss gently until the slices are well coated — being gentle prevents breakage in the beets.
5. Pour the remaining 1/4 cup (4 tablespoons) of cream into the bottom of the prepared baking dish. Sprinkle with 1/2 ounce grated Parmesan and the minced garlic so that the bottom layer starts flavorful and fragrant.
6. Assemble the gratin by grabbing small stacks of slices and standing them on a slight diagonal in the dish. Start at the top with a row of sweet potatoes, follow with a row of parsnips, then a row of beets. Repeat this pattern to create about six rows of vegetables across the dish. You want a snug fit so the gratin holds its shape during baking.
7. Season the top of the arranged vegetables with a final pinch of salt and pepper and sprinkle the remaining Parmesan over the surface.
8. Cover the baking dish tightly with aluminum foil and place it in the preheated oven. Bake for 30 minutes — this steams and softens the slices so they’ll be fork-tender.
9. Carefully remove the foil and top the gratin with the shredded Gruyère. Return the dish to the oven, uncovered, and bake for another 18–20 minutes, or until the vegetables are fully tender, the cheese has melted, and the top is lightly browned and bubbling.
10. Finish with a sprinkle of fresh thyme leaves and let the gratin rest 5 minutes before serving to allow the cream to settle.
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How to tell when the gratin is done
– Fork test: a fork should slide easily into the thickest slices of sweet potato and beet without resistance.
– Surface: the top should be golden-brown and the melted gruyère should be bubbling.
– Edges: small browned bits around the edge are a delicious sign the sugars in the vegetables have caramelized.
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Serving suggestions
This Cheesy Root Vegetable Gratin is an excellent side for roasted chicken, pork tenderloin, or a holiday ham. For a vegetarian plate, serve it alongside a simple green salad dressed in lemon vinaigrette and a warm grain like farro or barley. Leftovers are comforting — try reheating in a low oven (325°F) until warmed through, or slice and pan-fry pieces for a crisp edge.
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Variations and swaps
– Cheese: If you don’t have Gruyère, Emmental or a mild cheddar will work. For a sharper profile, try sharper cheddar or asiago.
– Milk swap: Whole milk can replace some or all of the cream, but the mixture won’t be as rich or set as densely.
– Herbs: Swap thyme for rosemary (use sparingly) or add a pinch of nutmeg for warmth.
– Add-ins: Thin slices of apple or pear can add a sweet-tart contrast; layer them thinly with the beets.
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Make-ahead, storage and reheat
– Make-ahead: Assemble the gratin and cover tightly with foil. Refrigerate up to 24 hours before baking. You may need to add 5–10 minutes to the baking time if baking from cold.
– Storage: Store leftovers in an airtight container in the refrigerator for up to 4 days.
– Reheat: Warm in a 325°F oven for 15–20 minutes or until heated through. For a faster method, reheat individual slices in a skillet over medium heat to crisp the edges.
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Troubleshooting
– Vegetables still firm after baking: They may have been sliced too thickly. Use a mandoline or slice thinner next time and extend the covered baking time by 10–15 minutes.
– Soggy top but undercooked center: Make sure you pre-coat and bake covered first to steam the interiors, then uncover long enough for the top to brown.
– Beets bleeding color: That’s normal and part of the charm, but you can par-cook beets briefly before slicing if you want to minimize staining other vegetables.
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Final thoughts
This Cheesy Root Vegetable Gratin is one of those recipes that looks like effort but comes together with simple techniques and a little patience. It celebrates the sweet, earthy flavors of root vegetables while leaning on rich cheese and cream for a comforting finish. Whether you’re feeding a holiday crowd or want an impressive weeknight side, this gratin reliably delivers.
If you try it, I’d love to hear how you layered your vegetables or what cheese swaps you made — leave a comment or tag me on Instagram. Happy cooking!
Cheesy Root Vegetable Gratin
Ingredients
Equipment
Method
- 1. Preheat the oven to 400°F (205°C) and grease a 3-quart baking dish with the softened butter. Make sure the butter reaches the sides so the cheese won’t stick later.
- 2. Slice the sweet potatoes, parsnips and beets into very thin rounds (about 1/16–1/8 inch). A mandoline makes this fast and consistent; if you’re using a knife, take your time and keep the slices even. Transfer each vegetable to its own bowl.
- 3. Divide the cream among the bowls: pour 4 tablespoons of cream over the sweet potatoes and 4 tablespoons over the parsnips, and 2 tablespoons over the beets. This partial pre-coating helps each vegetable absorb richness and salt.
- 4. To each bowl, add 1/2 ounce (about 1/2 cup grated) Parmesan and 1 teaspoon minced thyme. Season each bowl generously with salt and pepper. Toss gently until the slices are well coated — being gentle prevents breakage in the beets.
- 5. Pour the remaining 1/4 cup (4 tablespoons) of cream into the bottom of the prepared baking dish. Sprinkle with 1/2 ounce grated Parmesan and the minced garlic so that the bottom layer starts flavorful and fragrant.
- 6. Assemble the gratin by grabbing small stacks of slices and standing them on a slight diagonal in the dish. Start at the top with a row of sweet potatoes, follow with a row of parsnips, then a row of beets. Repeat this pattern to create about six rows of vegetables across the dish. You want a snug fit so the gratin holds its shape during baking.
- 7. Season the top of the arranged vegetables with a final pinch of salt and pepper and sprinkle the remaining Parmesan over the surface.
- 8. Cover the baking dish tightly with aluminum foil and place it in the preheated oven. Bake for 30 minutes — this steams and softens the slices so they’ll be fork-tender.
- 9. Carefully remove the foil and top the gratin with the shredded Gruyère. Return the dish to the oven, uncovered, and bake for another 18–20 minutes, or until the vegetables are fully tender, the cheese has melted, and the top is lightly browned and bubbling.
- 10. Finish with a sprinkle of fresh thyme leaves and let the gratin rest 5 minutes before serving to allow the cream to settle.
