Sweet Potato & Beet Gratin is a beautiful, comforting side dish layered with tender sweet potatoes, earthy beets, creamy Yukon Gold potatoes, and sweet sautéed onions. Everything is baked in a rich Parmesan cream sauce and finished with bubbling Gruyère, crispy fried onions, fresh thyme, and jewel-like pomegranate seeds.

It’s the kind of dish that instantly makes a dinner table feel special. Honestly, the combination of sweet potatoes and beets gives this gratin gorgeous colour and flavour, while the creamy sauce and golden cheese topping make every bite wonderfully cozy.

Ingredients

For the Gratin

2 large sweet potatoes (about 700 g), peeled and thinly sliced
3 medium beets (about 450 g), peeled and thinly sliced
2 large Yukon Gold potatoes (about 400 g), peeled and thinly sliced
1 small yellow onion, thinly sliced
2 tbsp olive oil
2 garlic cloves, minced
1 tsp fresh thyme leaves
1/2 tsp dried rosemary
1/2 tsp salt
1/4 tsp black pepper

For the Creamy Sauce

1 cup (240 ml) heavy cream
1/2 cup (120 ml) vegetable or chicken broth
1/2 cup (50 g) grated Parmesan cheese
1/2 tsp garlic powder
1/4 tsp nutmeg
1/2 tsp salt
1/4 tsp black pepper

For the Topping

1/2 cup (50 g) shredded Gruyère or mozzarella cheese
2 tbsp grated Parmesan cheese
2 tbsp crispy fried onions or shallots
1 tbsp fresh thyme leaves
1/4 cup (40 g) pomegranate seeds

How to Make It

1. Preheat the Oven

Preheat your oven to 375°F (190°C). Lightly grease a 9 × 13-inch (23 × 33 cm) baking dish with olive oil and set it aside.

2. Prepare the Vegetables

Peel the sweet potatoes, beets, and Yukon Gold potatoes. Using a sharp knife or mandoline, slice all the vegetables very thinly and as evenly as possible. Consistent slices help everything cook at the same rate and create a beautiful layered presentation.

3. Make the Cream Sauce

In a medium bowl, whisk together the heavy cream, vegetable or chicken broth, Parmesan cheese, garlic powder, nutmeg, salt, and black pepper until smooth and well combined.

4. Sauté the Onion and Garlic

Heat 1 tbsp olive oil in a skillet over medium heat. Add the sliced onion and cook for 4–5 minutes, stirring occasionally, until softened and lightly golden.

Add the minced garlic and fresh thyme and cook for another 30 seconds, just until fragrant. Remove from the heat.

5. Arrange the Vegetables

Arrange the sweet potato, beet, and Yukon Gold potato slices in alternating rows inside the prepared baking dish. Tuck some of the softened onions between the slices, spreading them as evenly as possible.

The alternating colours create a beautiful presentation while allowing each vegetable to contribute its own flavour and texture.

6. Add the Cream Sauce

Slowly pour the creamy Parmesan sauce evenly over the vegetables. Gently press the slices down if needed so the sauce can reach between the layers.

7. Cover and Bake

Cover the baking dish tightly with aluminum foil. Bake for 45 minutes, allowing the vegetables to steam gently in the creamy sauce and become tender.

8. Add the Cheese

Carefully remove the foil. Sprinkle the shredded Gruyère or mozzarella evenly over the top, followed by the remaining grated Parmesan cheese.

9. Finish Baking

Return the uncovered gratin to the oven and bake for another 25–30 minutes, until the vegetables are completely tender and the cheese is melted, bubbling, and golden brown.

10. Crisp the Topping

During the final 5 minutes of baking, sprinkle the crispy fried onions or shallots over the top. This allows them to become golden and crunchy without burning.

11. Rest the Gratin

Remove the gratin from the oven and let it rest for 10–15 minutes. Resting gives the creamy sauce time to settle and makes the layers easier to portion and serve.

12. Garnish and Serve

Finish with fresh thyme leaves and scattered pomegranate seeds. Serve warm as a festive holiday side dish, vegetarian centerpiece, or comforting addition to a family dinner.

Why This Recipe Works

This gratin brings together several different flavours and textures in one beautiful baking dish. Sweet potatoes provide natural sweetness and creamy tenderness, while beets add an earthy flavour and striking colour.

Yukon Gold potatoes help create a hearty, satisfying texture, while the sautéed onion and garlic add savoury depth. The Parmesan cream sauce brings everything together with a rich, silky consistency.

Then comes the golden cheese topping and crispy fried onions. The combination of creamy vegetables, bubbling cheese, crunchy shallots, and fresh pomegranate seeds makes this gratin especially memorable.

Tips for the Best Sweet Potato & Beet Gratin

Slice the vegetables evenly: Thin, consistent slices help the sweet potatoes, beets, and potatoes cook at the same rate.
Use a mandoline carefully: A mandoline makes quick work of slicing, but always use the safety guard and keep your fingers protected.
Don’t skip the foil: Covering the gratin during the first stage helps the vegetables become tender without drying out the top.
Let it rest: A 10–15 minute resting period allows the sauce to thicken slightly and makes serving much easier.
Add crispy onions near the end: This keeps them crunchy and prevents them from becoming too dark.
Use fresh pomegranate seeds: Their bright, juicy flavour provides a refreshing contrast to the rich cream and cheese.

Serving Suggestions

This sweet potato and beet gratin makes a wonderful side dish for roasted turkey, chicken, pork, or beef. Its colourful layers make it particularly suited to Thanksgiving dinners, Christmas meals, and other festive gatherings.

For a vegetarian meal, serve it alongside a crisp green salad, roasted Brussels sprouts, sautéed greens, or crusty artisan bread. The creamy gratin is filling enough to serve as the centerpiece of a meat-free dinner.

Frequently Asked Questions

Can I prepare this gratin ahead of time?

Yes. You can assemble the gratin several hours ahead, cover it tightly, and refrigerate it until you’re ready to bake. Allow the chilled dish a little extra time in the oven if necessary, and make sure the vegetables are completely tender before serving.

Can I use regular potatoes instead of Yukon Gold?

Yes. Russet or another waxy potato can work, although Yukon Gold potatoes provide a naturally creamy texture and buttery flavour that works particularly well in this gratin.

Can I use goat cheese instead of Gruyère?

Yes. Soft goat cheese can add a pleasant tangy flavour. For the best result, you can use a smaller amount of goat cheese together with Parmesan for a balanced topping.

How do I know when the gratin is done?

The gratin is ready when a thin knife slides easily through the thickest vegetable slices and the cheese on top is melted, bubbling, and golden.

Can I make this gratin vegetarian?

Absolutely. Use vegetable broth instead of chicken broth to keep the entire dish vegetarian.

Why should I let the gratin rest before serving?

Resting allows the creamy sauce to settle and thicken slightly. It also helps the vegetable layers hold together when you slice and serve the gratin.

Nutrition & Timing

Details	Amount
Prep Time	25 minutes
Cook Time	1 hour 15 minutes
Total Time	1 hour 40 minutes
Servings	8
Calories	Approx. 325 per serving
Protein	Approx. 9g per serving

Final Thoughts

Sweet Potato & Beet Gratin is a gorgeous twist on the classic creamy potato gratin. The combination of sweet potatoes, earthy beets, and Yukon Gold potatoes creates colourful layers that become incredibly tender beneath a rich Parmesan cream sauce.

The golden Gruyère topping, crispy fried onions, fresh thyme, and bright pomegranate seeds take it to another level. It’s comforting enough for a cozy family dinner but beautiful enough to deserve a place at any holiday table.