Cheesy Root Vegetable Gratin

This cheesy root vegetable gratin transforms humble roots into a stunning side dish worthy of your holiday table or Sunday dinner. The vibrant colors of sweet potatoes, parsnips, and beets create a beautiful presentation while the cream and cheese bring everything together in a decadent marriage of flavors and textures.

I first made this gratin for a Thanksgiving gathering where I needed a showstopping vegetarian option. The gorgeous rows of colorful vegetables earned so many compliments that it now appears at nearly every special occasion meal I host.

Ingredients

• Sweet potatoes: Provide natural sweetness and a vibrant orange color. Look for long, evenly shaped ones about 2 inches thick for uniform slices.
• Parsnips: Contribute a subtle sweetness with hints of spice. Choose firm, medium sized ones without soft spots.
• Beets: Offer earthy flavor and stunning ruby color. Select small to medium beets for less earthiness and faster cooking.
• Heavy cream: Creates the luscious sauce that binds everything together. The fat content ensures a silky texture that milk cannot achieve.
• Parmesan cheese: Adds savory depth and salty notes. Freshly grated works best for melting consistency.
• Fresh thyme: Brings an aromatic herbal note that cuts through the richness. Always opt for fresh over dried for brighter flavor.
• Gruyere cheese: Creates that irresistible golden brown top with nutty flavor. Splurge on good quality for the best melt.
• Butter: Prevents sticking and enriches the overall flavor profile. Use unsalted to control sodium levels.

Step-by-Step Instructions

Prepare the baking dish:

Preheat your oven to 400˚F and thoroughly coat a 3 quart baking dish with the softened butter. Make sure to get every corner to prevent any sticking issues later.

Slice the vegetables:

Use a mandoline to create extremely thin, consistent slices of sweet potatoes, parsnips, and beets. Aim for slices about 1/16 inch thick for even cooking. Keep each vegetable type separate in individual bowls to prevent color bleeding.

Season the vegetables:

Pour 4 tablespoons of cream over the sweet potatoes, 4 tablespoons over parsnips, and 2 tablespoons over beets. The beets need less cream as they contain more moisture. Add Parmesan and thyme to each bowl, followed by generous seasoning with salt and pepper. Gently toss each bowl to ensure all slices are evenly coated with the cream and seasonings.

Prepare the baking dish:

Pour the remaining quarter cup of cream into the bottom of your buttered baking dish. Sprinkle half an ounce of Parmesan and all of the minced garlic evenly across the cream. This creates a flavorful foundation that will bubble up through the vegetables as they cook.

Arrange the vegetables:

Starting at one end of the dish, take a stack of sweet potato slices and arrange them standing up on a slight angle. Follow with a row of parsnips, then a row of beets. Continue this pattern creating six alternating rows of vegetables. The slices should be packed tightly enough to support each other but not so tight that the cream cannot flow between them.

Initial baking:

Season the top with salt, pepper, and the remaining Parmesan cheese. Cover the dish tightly with foil and bake for a full 30 minutes. The foil traps steam which helps soften the vegetables without browning them too quickly.

Final browning:

Remove the foil and sprinkle the gruyere cheese evenly across the top. Return the dish to the oven uncovered and bake for another 18 to 20 minutes. Look for a golden brown top and vegetables that yield easily when pierced with a fork. The cream should be bubbling and thickened.

Garnish and serve:

Sprinkle fresh thyme leaves over the hot gratin just before serving for a burst of color and aroma. Let rest for 5 minutes before serving to allow the cream to set slightly.

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My favorite aspect of this dish is how the beets naturally dye the cream around them creating a gorgeous pink hue that contrasts with the orange sweet potatoes. When my niece first saw this at our table, she declared it rainbow food and now specifically requests her favorite colors whenever I make it.

Make Ahead Options

This gratin can be assembled up to 24 hours in advance and refrigerated covered with plastic wrap. Remove from refrigerator 30 minutes before baking to take the chill off. You may need to add 5 to 10 minutes to the covered baking time if starting with a cold gratin. This make ahead capability makes it perfect for holiday meals when oven space and time are at a premium.

Substitution Ideas

Feel free to customize this gratin with whatever root vegetables are available. Rutabaga adds peppery flavor while turnips bring pleasant bitterness. Yukon gold potatoes work beautifully in place of sweet potatoes for a more traditional flavor profile. For a dairy free version, coconut cream can substitute for heavy cream, though the flavor will shift slightly. Nutritional yeast can replace Parmesan for a vegan adaptation.

Serving Suggestions

This versatile gratin pairs beautifully with roasted meats, particularly herb roasted chicken or beef tenderloin. For a vegetarian meal, serve alongside a robust green salad with vinaigrette to cut through the richness. The gratin reheats beautifully and makes wonderful leftovers paired with a fried egg for brunch the next day. Consider serving individual portions in ramekins for an elegant plated presentation at dinner parties.

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This dish turns humble roots into an elegant, flavor-packed masterpiece perfect for any special occasion.

Frequently Asked Questions

→ Can I use different root vegetables for this gratin?

Yes! While sweet potatoes, parsnips and beets create a beautiful color contrast, you can substitute other root vegetables like carrots, turnips, rutabaga, or regular potatoes based on your preference or what you have available.

→ Can I make this gratin ahead of time?

You can assemble the gratin up to 24 hours in advance and refrigerate it covered. When ready to bake, allow it to sit at room temperature for 30 minutes before placing in the oven. You may need to add 5-10 minutes to the covered baking time.

→ What can I use instead of Gruyere cheese?

If Gruyere isn't available, you can substitute with Emmental, Jarlsberg, Swiss cheese, or even white cheddar. Each will provide a different but complementary flavor to the root vegetables.

→ Do I really need a mandoline to make this dish?

A mandoline makes it much easier to get uniformly thin slices, which ensures even cooking. If you don't have one, you can use a very sharp knife and slice the vegetables as thinly and evenly as possible.

→ Can I use milk instead of heavy cream?

As noted in the ingredients, you can substitute whole milk for heavy cream, but the final dish won't be as rich or creamy, and the sauce won't thicken as much during baking. Half-and-half would be a good middle-ground option.

→ How do I know when the gratin is done cooking?

The gratin is done when the vegetables are fork-tender (a fork easily pierces through), the cheese is melted, and the top has a light golden-brown color. If the top is browning too quickly but vegetables aren't tender yet, cover loosely with foil.