This decadent and deeply satisfying Root Vegetable Gratin is an absolute showstopper and you and yours are going to be thrilled to see it on your dinner table. It is as delicious and nourishing as it is gorgeous.
It’s also very low stress— you can make it a couple days before serving to help take the burden off of your day of holiday cooking, it reheats like a dream once you’re ready to serve.
Ingredient Substitutions
- No leeks? You can substitute white or yellow onion.
- Can’t find celery root, parsnips or sweet potatoes? Butternut squash or beets can also work well with the other veggies.
- No Gruyere? You can use more Parmigiano Reggiano, or Emmentaler.
Recipe Tips & FAQs
- It’s very helpful to have a mandoline for this recipe. The key to using one safely is to remember that the tip of whatever vegetable you’re slicing costs a lot less than an urgent care visit. Be safe and throw the veggie ends in your veggie stock.
- For those unfamiliar with leeks—you want to sauté the tender white stalk. The green tops are fibrous and hard to chew, but they hold a ton of flavor. Use some in the steeped cream, and save the rest for your next veggie, chicken or beef stock.
- The starch in the russet potatoes is the key to binding this gratin. By building every other layer of the gratin with potatoes you’ll ensure that it sets up perfectly.
- Celery root can be found at Dekalb Farmers Market; and sometimes at Whole Foods, Publix or Kroger. It’s also called celeriac.
- A dish like this always needs more salt than you think. Season your heavy cream and then make sure to season each layer of the gratin while you build it.
Serving Suggestions
- This gratin will be a welcome addition to any table during the holidays.
- Pair it with this Chicken & Wild Rice Soup for a cozy winter meal.
- It tastes great with this Roasted Pork Tenderloin.
- Alchemize your lunch hour with this Gratin and my Kale Salad recipe.
Storage and Shelf Life
Make Ahead: It’s best to make this recipe the day before you need it, as it will be much easier to serve once it has time to set up.
Refrigerate: Lasts for up to a week in an airtight container.
Freezer: Stores well in the freezer for 2 months.
Reheat Instructions
Preheat the oven to 350˚F and place the desired portion in an oven-safe dish. Reheat to an internal temperature of 165˚F. Time will vary depending on the quantity you reheat, but start checking after 10 minutes. If you’re reheating the entire gratin it will take an hour.
Final Thoughts
This is the recipe I always reach for whenever I’m catering a dinner party in the fall and winter. It’s a chic twist on a classic potato gratin and it always leaves my guests happy and satisfied. I love making it the day before—it gives me peace of mind the day of the event to know I’ve got a delicious gratin ready to rock so I can focus on making the rest of the meal great.
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Root Vegetable Gratin
Special Equipment
- 10 x 13-inch oven-safe casserole dish
- Japanese mandoline
Ingredients
- 4 cups heavy cream
- 2 garlic cloves peeled and crushed
- 4 sprigs fresh thyme
- ¼ teaspoon nutmeg ground
- 1 small bay leaf
- 1 teaspoon sea salt
- ¼ teaspoon black peppercorns
- 1 tablespoon butter unsalted
- 2 small leeks washed, dark green tops reserved, white parts sliced thinly (about 2 cups)
- 4 pounds russet potatoes peeled
- 1 ½ pound celery root peeled
- 1 ½ pound parsnips peeled
- 1 pound orange sweet potato peeled
- 1 pound purple sweet potatoes peeled
- 2 cups grated Parmigiano Reggiano
- 1 cup grated Gruyere (3 ounces)
- salt and freshly ground black pepper to taste
Instructions
- Cook the Leeks: Split the 2 leeks in half lengthwise. Wash well between all the layers, and slice thinly. Melt 1 tablespoon of butter in a medium-sized skillet over medium heat. Add the sliced leeks, season with salt and pepper, and cook, stirring often, until tender but not brown, about 5 minutes. Remove from the heat and reserve.
- Steep the Cream: In a 1-quart heavy-bottomed sauce pot, heat 4 cups heavy cream, 2 garlic cloves, 4 sprigs fresh thyme, ¼ teaspoon ground nutmeg, 1 bay leaf, a handful of washed green leek tops, 1 teaspoon sea salt and ¼ teaspoon black peppercorns to a simmer. Let the cream simmer while you build your gratin.
- Preheat the oven to 350˚.
- Build the Gratin: As you start to assemble the gratin, slice each vegetable layer right before you add it to the dish. This keeps the potatoes and other roots from oxidizing and turning brown while they sit.
- Shingle a layer of russet potato slices on the bottom of a 10×13 oven-safe casserole dish, then sprinkle generously with parmesan and a small amount of the leeks, and season with salt and pepper. Repeat this process with the other root vegetables, making sure that every other layer is sliced potatoes. Alternate with a layer of celery root, then potatoes, then sweet potatoes, then potatoes, then parsnips, then potatoes. Any extra root vegetable slices can be used to create a pretty pattern on top.
- Strain the cream and gently pour it over the gratin, being careful not to disrupt the layers. Sprinkle the gruyere on top.
- Bake the Gratin: Set the gratin dish on a large rimmed baking sheet and cover tightly with a layer of parchment paper, then foil.
- Bake for 2 hours total, removing the foil and parchment after an hour and a half, and continue baking until the top is golden brown and the sauce is bubbling, about 30 minutes.
- Serve: Allow it to rest at least 45 minutes before serving. I prefer to make this gratin a day ahead and then reheat before serving, as it looks prettier and holds together better that way. There’s no need to rest it for 45 minutes when reheating.
Hi, I’m Julia.
I’m a chef and wellness advocate passionate about helping others live well through nourishing food. I trained at the Culinary Institute of America and now work as a personal chef and community food advocate in Atlanta.
Want to know what inspired me to start Everyday Alchemy? Click the link icon below to read more.