I love bringing this Cheesy Root Vegetable Gratin to the Thanksgiving table because it turns humble root vegetables into a cozy, bubbling side dish. Thinly sliced potatoes, sweet potatoes, and parsnips bake in a fragrant cream sauce beneath a golden layer of cheese.
Why You’ll Love This Cheesy Root Vegetable Gratin
This gratin is hearty enough to feel special, yet simple to prepare with familiar ingredients. The vegetables become tender as they bake, while garlic, thyme, and two kinds of cheese add savory flavor. You can assemble it ahead, too, which is especially handy when the oven is busy on Thanksgiving.
Cheesy Root Vegetable Gratin Ingredients & Substitutions
- 1 tablespoon unsalted butter, for greasing the baking dish
- 1 pound russet potatoes, peeled and thinly sliced
- 1 pound sweet potatoes, peeled and thinly sliced
- 1 pound parsnips, peeled and thinly sliced
- 1 1/2 cups heavy cream
- 1/2 cup whole milk
- 2 garlic cloves, finely grated or minced
- 1 teaspoon fresh thyme leaves, plus extra for garnish
- 1 teaspoon kosher salt
- 1/2 teaspoon black pepper
- 1 cup shredded Gruyere cheese
- 1 cup shredded sharp cheddar cheese
Russet potatoes hold their shape nicely, but Yukon Gold potatoes work well, too. You can swap the parsnips for thinly sliced carrots or celery root. For a milder cheese flavor, use extra Gruyere in place of some or all of the cheddar.
Step-by-Step Instructions to Make Cheesy Root Vegetable Gratin
1. Prepare the baking dish
Heat the oven to 375°F (190°C). Grease a 9-by-13-inch baking dish with the butter. If your vegetable slices are not already prepared, peel and slice them into even rounds about 1/8 inch thick.
2. Make the cream mixture
In a bowl, whisk together the heavy cream, milk, garlic, thyme, salt, and black pepper.
3. Layer the vegetables
Arrange the potato, sweet potato, and parsnip slices in overlapping layers in the prepared dish. Pour the cream mixture evenly over the vegetables, then gently press the top layer down so it is lightly coated.
4. Bake until tender
Cover the dish tightly with foil and bake for 45 minutes. Carefully remove the foil and check the vegetables with a thin knife. If they still feel firm, cover and bake for another 10 to 15 minutes.
5. Add cheese and finish baking
Sprinkle the Gruyere and cheddar evenly over the top. Bake uncovered for 20 to 25 minutes, until the vegetables are tender and the cheese is golden and bubbling. Rest for 10 minutes before serving so the creamy layers can settle.
Tips for Success
- Slice the vegetables evenly so they cook at the same rate. A mandoline can help, but use its safety guard.
- Layer the slices fairly snugly, but avoid packing them so tightly that the cream cannot flow between them.
- Cover the dish securely during the first part of baking to help the vegetables soften without drying out.
- Let the gratin rest before scooping. The sauce thickens slightly as it cools.
- If the cheese browns before the vegetables are tender, loosely cover the top with foil and continue baking.
Variations of Cheesy Root Vegetable Gratin
For an earthier flavor, add a layer of thinly sliced celery root or turnips. A pinch of freshly grated nutmeg in the cream mixture brings gentle warmth, while a little chopped rosemary can take the place of some of the thyme. For a crisp finish, combine 1/3 cup plain breadcrumbs with a tablespoon of melted butter and scatter them over the cheese before the final bake.
Serving Suggestions: What to Pair with Cheesy Root Vegetable Gratin
This gratin makes a lovely Thanksgiving side alongside roast turkey, green beans, roasted Brussels sprouts, or a crisp autumn salad. It also pairs well with a simple roast chicken or lentil loaf for a comforting dinner. Because it is rich and creamy, I like to serve it with at least one bright vegetable dish on the table.
Storage & Reheating Instructions
Cool leftovers, then cover and refrigerate them for up to 4 days. Reheat individual portions in the microwave, or warm the covered baking dish in a 350°F (175°C) oven until heated through. For a little crispness on top, uncover the dish for the final few minutes. You can assemble the gratin a day ahead, cover it, and refrigerate it before baking. Let the dish sit at room temperature for about 20 minutes while the oven heats, then bake as directed, allowing extra time if it is still cold in the center.
Memories Made Around the Table
I like to bring this gratin to the table while it is still bubbling, with a few thyme leaves scattered over its golden top. It is the kind of side dish that invites everyone to take another spoonful, and I always appreciate how easily it fits beside the familiar Thanksgiving favorites.
FAQs
Can I make Cheesy Root Vegetable Gratin ahead?
Yes. Assemble it, cover it, and refrigerate it for up to a day before baking. Let it stand at room temperature for about 20 minutes before it goes into the oven, and allow extra baking time as needed.
How do I know when the vegetables are cooked?
Slide a thin knife into the center of the dish. It should pass through the thickest vegetable slices easily. If they are still firm, cover the gratin and bake a little longer before adding the cheese.
Can I use different root vegetables?
Yes. Thinly sliced Yukon Gold potatoes, carrots, celery root, or turnips can be used in place of some of the vegetables. Keep the slices a similar thickness so they bake evenly.
Can I freeze leftovers?
You can freeze portions in airtight containers for up to 2 months, though the cream sauce may become a little less smooth after thawing. Thaw overnight in the refrigerator and reheat covered in the oven.
Final Thoughts
Cheesy Root Vegetable Gratin is a comforting, make-ahead-friendly side that brings color and plenty of cozy flavor to Thanksgiving dinner. Serve it warm, let everyone dig into those creamy layers, and save any leftovers for an easy next-day meal.
Root Vegetable Gratin
Equipment
- 1 9 by 13 inch baking dish
- 1 Aluminum foil
- 1 Mandoline Optional; use the safety guard.
Ingredients
- 1 tablespoon unsalted butter for greasing the baking dish
- 1 pound russet potatoes peeled and thinly sliced
- 1 pound sweet potatoes peeled and thinly sliced
- 1 pound parsnips peeled and thinly sliced
- 1.5 cups heavy cream
- 0.5 cup whole milk
- 2 cloves garlic finely grated or minced
- 1 teaspoon fresh thyme leaves plus extra for garnish
- 1 teaspoon kosher salt
- 0.5 teaspoon black pepper
- 1 cup shredded Gruyere cheese
- 1 cup shredded sharp cheddar cheese
Instructions
- Heat the oven to 375°F. Grease a 9-by-13-inch baking dish with the butter. Peel and slice the vegetables into even rounds about 1/8 inch thick if they are not already prepared.
- In a bowl, whisk together the heavy cream, milk, garlic, thyme, salt, and black pepper.
- Arrange the potato, sweet potato, and parsnip slices in overlapping layers in the prepared dish. Pour the cream mixture evenly over the vegetables, then gently press the top layer down so it is lightly coated.
- Cover the dish tightly with foil and bake for 45 minutes. Carefully remove the foil and check the vegetables with a thin knife. If they still feel firm, cover and bake for another 10 to 15 minutes.
- Sprinkle the Gruyere and cheddar evenly over the top. Bake uncovered for 20 to 25 minutes, until the vegetables are tender and the cheese is golden and bubbling. Rest for 10 minutes before serving.