Cheesy Root Vegetable Gratin is a cozy and comforting dish that combines tender, roasted root vegetables with a rich, bubbly cheese topping. It’s got a mix of earthy flavors from carrots, parsnips, and potatoes, all wrapped up in a creamy sauce that’s just the right amount of cheesy and golden on top.
I love making this gratin when I want something warm and satisfying but still a little fancy for dinner. It’s one of those recipes that feels like a special treat but is pretty simple to throw together. I usually use whatever root vegetables I have on hand, and I think the variety makes each bite a little surprise.
My favorite way to serve this is alongside a fresh green salad or some roasted chicken. It’s great for cozy weeknights or even holiday dinners because it’s filling without being heavy. Plus, leftovers are wonderful the next day—just pop them back in the oven to warm up and get that cheese melty again.
Key Ingredients & Substitutions
Sweet Potatoes: These add natural sweetness and a soft texture when baked. If you don’t have sweet potatoes, butternut squash makes a lovely substitute with a similar sweetness.
White and Purple Potatoes: White potatoes give a creamy texture, while purple potatoes add color and a slightly earthier flavor. You can swap any of these with other firmer root veggies like turnips or celeriac.
Gruyère Cheese: It melts beautifully and adds a nutty, rich flavor to the gratin. Parmesan mixed in brings extra sharpness. If you prefer, use cheddar or fontina for different but tasty results.
Heavy Cream: This creates the creamy sauce that binds all the veggies together. For a lighter version, try half-and-half or whole milk with a little butter added.
Fresh Thyme & Garlic: These herbs build the flavor base. Rosemary or sage can be great alternatives if you want to change things up.
How Do You Get Perfectly Tender Layers and a Crispy Cheese Top?
Getting the gratin creamy inside and golden on top means baking it in two stages.
- Step 1: Cover the dish to trap steam—this steams the vegetables, making them tender without drying out.
- Step 2: Remove the foil and add extra cheese on top to brown and crisp up, giving you that satisfying crunchy topping.
Pro tip: Slice the veggies evenly, about ⅛ to ¼ inch thick. If they’re too thick, they’ll take longer to cook and might stay a bit firm. Use a mandoline if you have one—it makes uniform slices fast and safe.
Also, letting the gratin rest after baking helps the sauce thicken and the flavors settle. This way, it’s easier to serve and tastes even better.
Equipment You’ll Need
- Mandoline slicer – helps you slice root vegetables thin and even for even cooking.
- Oven-safe baking dish – a ceramic or glass dish works great for steady, even heat and easy serving.
- Small saucepan – to gently warm the cream and infuse it with garlic and herbs.
- Wooden spoon or silicone spatula – for mixing and pouring the cream sauce without scratching your pan.
- Aluminum foil – to cover the dish while baking and keep moisture in for tender veggies.
Flavor Variations & Add-Ins
- Add cooked crumbled bacon or pancetta for a smoky, salty twist that pairs well with the creamy sauce.
- Mix in chopped fresh rosemary or sage instead of thyme for a different herbal flavor profile.
- Combine shredded sharp cheddar with Gruyère for a more pronounced cheese flavor and a vibrant color on top.
- Include thin slices of fennel or leek in the layers for a subtle oniony sweetness and extra texture.
Cheesy Root Vegetable Gratin
Ingredients You’ll Need:
Vegetables:
- 2 medium sweet potatoes (orange-fleshed), peeled and thinly sliced
- 2 medium white potatoes, peeled and thinly sliced
- 2 medium purple potatoes (or any purple root vegetable like beet), peeled and thinly sliced
Cream & Cheese:
- 2 cups heavy cream
- 1 cup grated Gruyère cheese (or a mix of Gruyère and Parmesan)
Flavorings & Others:
- 2 cloves garlic, minced
- 1 tsp fresh thyme leaves (plus extra for garnish)
- Salt and freshly ground black pepper, to taste
- 2 tbsp unsalted butter, for greasing the baking dish and dotting on top
Time Needed:
This delicious gratin takes about 15 minutes to prepare and slice your vegetables, plus about 1 hour baking time (40 minutes covered, then 20-25 minutes uncovered). Allow 10 minutes resting time before serving. Total time is approximately 1 hour 25 minutes.
Step-by-Step Instructions:
1. Get Your Oven Ready
Preheat your oven to 375°F (190°C). Butter your baking dish well so the gratin won’t stick.
2. Warm the Cream with Herbs and Garlic
In a small saucepan, gently heat the heavy cream with minced garlic and thyme leaves until warm but not boiling. Season with salt and pepper. Turn off the heat and set aside.
3. Arrange the Vegetables in the Dish
Layer the thin slices of sweet potatoes, white potatoes, and purple potatoes in the buttered baking dish in rows or alternating patterns. Slightly overlap each slice to create an even layer.
4. Add Cream and Cheese
Pour the warmed cream mixture evenly over the layered vegetables. Then, sprinkle ¾ cup of the grated Gruyère cheese evenly on top.
5. Add Butter and Cover
Dot the top with small spoonfuls of butter. Cover the dish tightly with aluminum foil to keep moisture in for tender vegetables.
6. Bake Covered and Then Uncovered
Bake the gratin covered for 40 minutes. Remove the foil, sprinkle the remaining ¼ cup cheese over the top, and bake uncovered for an additional 20-25 minutes until the top is golden, bubbly, and the vegetables are tender when you pierce them with a fork.
7. Rest and Serve
Let the gratin sit for about 10 minutes to thicken up and let the flavors meld. Garnish with fresh thyme leaves if you like, then serve warm and enjoy!
Can I Use Frozen Root Vegetables for This Gratin?
Yes, you can, but make sure to thaw and pat them dry first to avoid excess moisture, which can make the gratin watery. Slightly reduce the cream to balance the extra moisture.
How Should I Store Leftovers?
Store any leftovers in an airtight container in the fridge for up to 3 days. Reheat in the oven at 350°F (175°C) until warmed through to keep the cheese topping nice and melty.
Can I Substitute the Cheese?
Absolutely! While Gruyère adds a lovely nutty flavor, you can swap in cheddar, fontina, or a mix of Parmesan and mozzarella for a different but delicious cheesy twist.
Is There a Way to Make This Dish Lighter?
Try using half-and-half or whole milk instead of heavy cream, and reduce the butter slightly. Keep in mind this may make the gratin less rich and creamy but still tasty!
