Cheesy Root Vegetable Gratin: A Stunning Holiday Side Dish

When you’re looking for a show-stopping side dish that delivers on both flavor and presentation, this cheesy root vegetable gratin is your answer. Layers of tender sweet potatoes, earthy parsnips, and vibrant beets come together in a luxurious cream sauce, topped with melted Gruyère cheese that creates an irresistible golden crust.

This root vegetable gratin transforms humble winter vegetables into an elegant masterpiece worthy of your holiday table. Whether you’re planning Thanksgiving dinner, hosting Christmas guests, or simply craving comfort food that looks as good as it tastes, this recipe delivers every time. The best part? It’s surprisingly simple to prepare, especially with a few pro tips to ensure perfect results.

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Why This Root Vegetable Gratin Recipe Works

What makes this cheesy root vegetable gratin truly special is the thoughtful combination of flavors and textures. Sweet potatoes bring natural sweetness and a creamy texture when baked. Parsnips add subtle earthiness with a hint of nuttiness that complements the other vegetables beautifully. Beets contribute gorgeous color and a slightly sweet, earthy depth that ties everything together.

The cream sauce infused with garlic, fresh thyme, and Parmesan creates a rich base that brings cohesion to the dish. Topping everything with Gruyère cheese adds that final touch of nutty, melty perfection. When baked, the vegetables become fork-tender while the top develops a golden-brown crust that’s absolutely addictive.

This gratin also offers impressive visual appeal. When you arrange the thinly sliced vegetables standing upright in rows, you create a stunning presentation that makes guests think you spent hours on this dish—when in reality, it comes together quite easily.

Ingredients You’ll Need

For a successful root vegetable gratin, gather these simple ingredients:

For the Vegetables:

• 1-2 long sweet potatoes (about 2 inches thick), peeled
• 3-4 large parsnips, trimmed and peeled
• 3-5 small beets, peeled
• 1 tablespoon unsalted butter for greasing

For the Cream Mixture:

• 14 tablespoons heavy cream, divided
• 4 ounces grated Parmesan cheese, divided
• 1 tablespoon fresh minced thyme, divided
• 1 garlic clove, minced
• 1 ounce shredded Gruyère cheese
• Salt and black pepper to taste

The ingredient quantities are designed for a 3-quart baking dish. The ranges given for vegetables account for different sizes and shapes of both the vegetables and your baking dish.

Essential Equipment for Success

Having the right tools makes this recipe much easier:

• Mandoline slicer – This is the secret weapon for achieving uniformly thin slices quickly. Consistent thickness ensures even cooking throughout the gratin.
• 3-quart oval baking dish – The classic shape for this recipe, though rectangular works too.
• Three mixing bowls – For coating each vegetable type separately.
• Vegetable peeler – For preparing your root vegetables.
• Kitchen gloves – Essential when handling beets to prevent staining.
• Aluminum foil – For covering during the initial baking phase.

If you don’t have a mandoline, a very sharp knife and patience will work—just focus on keeping slices as uniform as possible.

Step-by-Step Instructions

Preparing Your Vegetables

Start by preheating your oven to 400°F. Generously grease your 3-quart baking dish with softened butter, making sure to coat the bottom and sides completely.

Using your mandoline or sharp knife, slice the sweet potatoes, parsnips, and beets into very thin rounds—aim for about 1/8 inch thickness. This thinness is crucial for proper cooking and that beautiful presentation. Transfer each type of vegetable to its own mixing bowl.

Coating the Vegetables

Here’s where the magic begins. Pour 4 tablespoons of heavy cream over the sweet potatoes and another 4 tablespoons over the parsnips. For the beets, use only 2 tablespoons of cream—this is important for preventing color bleeding.

Add half an ounce of grated Parmesan and one teaspoon of minced thyme to each bowl. Season each bowl generously with salt and freshly cracked black pepper. Gently toss until every slice is well coated with the cream mixture.

Building Your Gratin

Pour the remaining quarter cup of cream into the bottom of your prepared baking dish. Sprinkle with half an ounce of Parmesan and the minced garlic, spreading them evenly across the cream layer.

Now for the beautiful part: creating those gorgeous rows. Grab a stack of sweet potato slices and arrange them standing upright at an angle (on a bias) in the baking dish. Follow with a row of parsnips, then a row of beets. Continue this pattern, alternating vegetables until you’ve created six rows that fill your dish. The slices should be snug but not overly compressed.

Season the top of your assembled gratin with additional salt, pepper, and a final sprinkle of the remaining Parmesan.

Baking to Perfection

Cover the baking dish tightly with aluminum foil. This creates a steaming environment that helps the vegetables become tender without drying out. Bake for 30 minutes or until the vegetables feel soft when tested with a fork.

Remove the foil and sprinkle the shredded Gruyère cheese evenly over the top. Return the uncovered gratin to the oven and bake for an additional 18 to 20 minutes. You’re looking for fork-tender vegetables, completely melted cheese, and a lightly browned top.

Finish with a sprinkle of fresh thyme leaves before serving warm.

Pro Tips for Perfect Results Every Time

Preventing Beet Bleeding: The key to maintaining those distinct, colorful layers is using less cream on the beets. Too much cream causes the beet color to spread throughout the dish. While this doesn’t affect flavor, it does impact presentation. Also, make sure the bottom cream layer is thin—just enough to coat the dish.

Achieving Even Cooking: Uniform slice thickness is your best friend here. This ensures all vegetables cook at the same rate. If some slices are thicker than others, you’ll end up with some pieces that are mushy while others remain undercooked.

Handling Beets: Always wear kitchen gloves when working with beets. If you do get stains on your hands, create a paste with baking soda and warm water, then scrub vigorously. You may need to repeat this process.

Covering Technique: Wrap the foil tightly around your baking dish to trap steam effectively. This moisture helps soften the vegetables before the final uncovered bake that creates the golden top.

Make-Ahead Instructions

This root vegetable gratin is perfect for holiday meal prep. You can assemble the entire dish up to one day in advance, cover it tightly with foil, and refrigerate. When ready to bake, add an extra 5 to 7 minutes to the covered baking time to account for the cold temperature.

Keep in mind that making this ahead increases the risk of beet color bleeding since the vegetables sit longer in the cream. The flavor remains excellent, but the visual separation between vegetables may be less distinct.

Delicious Variations to Try

Herb Alternatives: While thyme is classic, feel free to experiment with fresh rosemary, sage, chives, or green onions. A combination of herbs works beautifully too.

Cheese Substitutions: Don’t have Gruyère? Try fontina, Swiss, Comté, Gouda, or even a mild cheddar. Each brings its own character to the dish.

Different Root Vegetables: Turnips and rutabaga are excellent alternatives. You could also add or substitute with thick carrots—just choose the largest ones available to match the size of other vegetables.

Dairy Adjustments: Whole milk or half-and-half can replace heavy cream if you prefer a lighter dish. Note that the sauce will be thinner and won’t reduce as much during baking.

Serving Suggestions

This cheesy root vegetable gratin pairs wonderfully with roasted meats, making it ideal for holiday dinners. Serve it alongside herb-crusted prime rib, roasted turkey, honey-glazed ham, or even a simple roasted chicken for Sunday dinner.

The rich, creamy nature of the gratin means it works best with dishes that have bright or acidic components to balance the richness. Consider pairing it with cranberry sauce, a crisp green salad, or roasted Brussels sprouts with balsamic glaze.

Storage and Reheating

Store leftover gratin in an airtight container in the refrigerator for up to three days. To reheat, cover with foil and warm in a 350°F oven for about 15 to 20 minutes, or until heated through. The microwave works in a pinch, though the oven method better maintains the texture.

Frequently Asked Questions

Can I slice the vegetables ahead of time? Yes, but store them in bowls covered with damp paper towels in the refrigerator for no more than a few hours before assembling. This prevents browning and drying.

Do the vegetables need to stand upright? While the upright presentation is stunning, you can absolutely layer the vegetables flat if that’s easier for you. The flavor will be identical.

Why is my gratin watery? This usually happens when too much cream is used or the gratin needs more uncovered baking time to allow excess liquid to evaporate and thicken.

Can I use other types of potatoes? While sweet potatoes work best for this recipe due to their sweetness and texture, you could use Yukon gold or red potatoes as an alternative.