Easy Cheesy Root Vegetable Gratin for Thanksgiving

I bought six pounds of assorted winter vegetables, looked them dead in the eye, and realized I had no plan for dinner. My mother-in-law arrived in two hours for our annual pre-holiday meal, so I needed a cheesy root vegetable gratin that looked deliberate instead of panicked.

My first attempt used thick slices and produced crunchy vegetables under melted cheese. Thin slices changed everything. Sweet potatoes, parsnips, and beets bake in heavy cream with Parmesan, garlic, thyme, and Gruyère until the edges turn tender and the top browns. This layered side dish makes a full baking dish of winter vegetables feel ready for a holiday table.

Why You’ll Love This Recipe

• Looks impressive: You arrange thin vegetable slices in a baking dish and let the oven handle the work.
• Frees up stove space: The oven cooks the vegetables while you manage the rest of dinner.
• Clears the crisper drawer: This easy layered root vegetable gratin recipe uses sweet potatoes, parsnips, and beets.
• Feeds a crowd: You can double the root vegetables without doubling the grocery budget.
• Creamy and savory: Heavy cream, Parmesan, garlic, thyme, and Gruyère create the sauce and browned top.

Tools You’ll Need

Nothing fancy, I promise.

• Mandoline slicer: Use a mandoline to cut thin, even rounds.
• 3-quart baking dish: An oval dish looks nice, but a rectangular dish holds the same amount.
• Aluminum foil: Foil traps steam so the vegetables soften during the first bake.
• Mixing bowls: Use separate bowls to season the sweet potatoes, parsnips, and beets.
• Cheese grater: Grate the Parmesan and Gruyère before you assemble the dish.

Ingredients

• 1 tablespoon unsalted butter – For greasing the pan so you do not spend an hour scrubbing baked-on cream later.
• 1-2 long sweet potatoes – Bring a natural sweetness that balances the earthy flavors of the other vegetables.
• 3-4 large parsnips – Add a slightly nutty, spiced flavor to the dish.
• 3-5 small beets – Provide a deep, earthy flavor and a striking color contrast.
• 14 tablespoons heavy cream – This is not the time to worry about your waistline, because skim milk just curdles in the oven.
• 4 ounces grated Parmesan – Adds a sharp, salty bite that balances the natural sugars of the root vegetables.
• 1 tablespoon fresh minced thyme – Brings a piney, earthy note that makes the whole house smell incredible.
• 1 garlic clove – Minced fresh garlic cuts through the rich dairy and gives the dish a necessary savory backbone.
• 1 ounce shredded gruyere – The ultimate melting cheese that gets bubbly and golden brown. Read up on Gruyère cheese if you want to know why it melts so perfectly.
• Salt and pepper – Be generous here, because potatoes absorb salt like a sponge and will taste completely flat if you skimp.

How To Make Cheesy Root Vegetable Gratin

Let the oven do the hard work while you go pour yourself a glass of wine.

1. Prep the oven and dish: Preheat your oven to 400 degrees Fahrenheit and generously butter your baking dish. Do not skip the butter, or you will be chiseling baked cream off ceramic until midnight.
2. Slice the vegetables: Slice the sweet potatoes, parsnips, and beets into very thin rounds and put each vegetable in its own bowl. I highly recommend wearing gloves for the beets unless you want your hands to look like a crime scene.
3. Season and coat: Pour four tablespoons of cream over the sweet potatoes and parsnips, and two tablespoons over the beets, then toss each with Parmesan, thyme, salt, and pepper. If you do not season each bowl individually, you end up with bland pockets of sadness in the middle of your dish.
4. Prep the base: Pour the remaining quarter cup of cream into the bottom of the baking dish and sprinkle it with Parmesan and minced garlic. This creates a bubbling sauce layer that prevents the bottom vegetables from drying out.
5. Arrange the slices: Grab a stack of sweet potatoes and line them standing up on a bias, followed by parsnips, then beets, repeating until you fill the dish. If your rows look a little crooked, just remember that melted cheese covers all visual imperfections.
6. Bake covered: Season the top with more salt, pepper, and Parmesan, then cover tightly with foil and bake for 30 minutes. The foil traps the steam, and if you peek too early, all that precious steam escapes.
7. Melt the cheese: Uncover the gratin, top it with the shredded Gruyère, and bake for another 18 to 20 minutes until the vegetables are fork-tender and the cheese is browned. Let it sit for a few minutes before serving so you do not burn the roof of your mouth.

Seasoning and Taste as You Go

Root vegetables need aggressive seasoning to wake up. Taste a tiny piece of potato before serving to check your balance.

• Too flat: Add a final sprinkle of flaky sea salt.
• Too salty: Serve the gratin with an unseasoned protein.
• Needs depth: Add a small pinch of nutmeg or extra fresh thyme over the top.

Make It Yours

You can easily adapt this easy layered root vegetable gratin recipe to fit what you have in the fridge.

• Different root vegetables: Swap the parsnips for rutabaga or turnips, though they take slightly longer to tenderize.
• Cheese swaps: If you cannot find Gruyère, a good quality Swiss or fontina melts just as beautifully.
• Herb variations: Rosemary or sage works perfectly if you do not have fresh thyme on hand.
• Add some crunch: Top the whole thing with toasted panko breadcrumbs during the last five minutes of baking for a textural contrast.

Perfect Pairings

This holiday side dish gratin needs a strong supporting cast to make it a full meal.

• Crusty sourdough bread mops up the garlic cream sauce.
• A crisp green salad with sharp vinaigrette cuts through the rich dairy.
• A dry white wine balances the earthy sweetness of the beets and sweet potatoes.

Cheesy Root Vegetable Gratin

This cheesy root vegetable gratin layers sweet potatoes, parsnips, and beets with heavy cream, Parmesan, garlic, thyme, and browned Gruyère. The covered bake at 400°F softens the vegetables, then the uncovered finish gives the cheese its golden crust. Serve this cheesy root vegetable gratin as a Thanksgiving root vegetable side dish, a Christmas side, or a Sunday dinner centerpiece.

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Prep Time 15 minutes mins

Cook Time 50 minutes mins

Total Time 1 hour hr 5 minutes mins

Servings: 8 servings

Course: Side Dish

Cuisine: French

Calories: 265

Ingredients Equipment Method Notes

Ingredients

  

• 1 tablespoon unsalted butter (softened)
• 1-2 l ong sweet potatoes (about 2 inches thick) peeled
• 3-4 large parsnips ends trimmed and peeled
• 3-5 small beets peeled
• 14 tablespoons heavy cream divided ((whole milk is fine, but mixture won't thicken as much or be as creamy))
• 4 ounces grated Parmesan divided
• 1 tablespoon fresh minced thyme divided (plus more for garnish)
• 1 g arlic clove minced
• 1 ounce shredded gruyere
• salt and pepper to taste

Equipment

• Mandoline slicer
• 3-quart baking dish
• Aluminum foil
• Cheese grater

Method

 

1. Prepare the Oven and Baking Dish

   Preheat the oven to 400°F (200°C). Generously butter a 3-quart baking dish, making sure the bottom and sides are well coated to prevent sticking.
2. Slice the Vegetables

   Using a sharp knife or mandoline, slice the sweet potatoes, parsnips, and beets into very thin, evenly sized rounds. Keeping the slices similar in thickness helps the vegetables cook at the same rate.

   Place each vegetable in a separate bowl. If using fresh beets, consider wearing gloves while handling them to prevent their natural color from staining your hands.
3. Season the Vegetables

   Pour 4 tablespoons of cream over the sweet potatoes and parsnips. Pour 2 tablespoons of cream over the beets.

   Add Parmesan cheese, thyme, salt, and black pepper to each bowl. Gently toss the vegetables until the slices are evenly coated with the cream and seasonings.
4. Prepare the Creamy Base

   Pour the remaining ¼ cup of cream into the bottom of the prepared baking dish. Sprinkle the cream evenly with Parmesan cheese and minced garlic.
5. Arrange the Vegetable Slices

   Begin arranging the vegetables in the baking dish. Stand a stack of sweet potato slices upright at a slight angle, then add slices of parsnip followed by beet slices.

   Continue alternating the vegetables in the same pattern until the entire dish is filled. Keep the slices standing closely together so the gratin holds its shape while baking.
6. Bake Covered

   Season the arranged vegetables with additional salt and black pepper, then sprinkle more Parmesan over the top.

   Cover the baking dish tightly with aluminum foil. Bake for 30 minutes, allowing the vegetables to steam and begin softening in the creamy mixture.
7. Add the Gruyère and Finish Baking

   Carefully remove the foil and sprinkle the shredded Gruyère evenly over the top.

   Return the uncovered dish to the oven and bake for another 18–20 minutes, or until the vegetables are fork-tender and the Gruyère is fully melted, bubbling, and lightly browned.
8. Rest and Serve

   Remove the gratin from the oven and let it rest for a few minutes before serving. This allows the creamy sauce to settle and makes the gratin easier to portion.

Recipe Notes

Yield: Makes 1 3-quart casserole.

Nutrition: Nutrition information is based on the lowest quantity of vegetables listed in the ingredient ranges.

Make Ahead: The gratin can be prepared up to 1 day ahead. Cover tightly with foil and refrigerate. When ready to bake, place the covered gratin directly in the oven and add about 5–7 minutes to the covered baking time.

Beet Color: Preparing the gratin ahead can cause the beets to bleed their color into the cream. This does not affect the flavor, but it may change the appearance of the finished dish.

Prevent Beet Bleeding: Coat the sliced beets only lightly with cream. They should be covered enough to prevent them from drying out during baking, but avoid using excess cream.

Creamy Base: The bottom of the baking dish should have only a thin layer of cream topped with Parmesan. The exact amount may vary slightly depending on the surface area of your baking dish, so use just enough to lightly coat the bottom.