This heavenly, garlic-infused Sweet Potato Gratin is a delicious choice for the holidays. Thinly sliced sweet potatoes and buttery Yukon gold potatoes are layered with Gruyère and Parmesan cheese and baked until golden brown.
Sweet potatoes are on the menu all year long in this house. We love them mashed, roasted, and baked, but this Sweet Potato Gratin has a permanent place on my holiday menus.
Heavenly is not too strong a word to describe this Sweet Potato Gratin. If you try it, I’m pretty sure you will agree. But, in addition to being delicious, I love the simplicity of it.
It has a manageable list of ingredients and it’s quite easy to put together with the tips and tricks that I’m sharing with you today.
You can get some of the prep out of the way in advance, or you can get the whole thing done and set it in the fridge to rest until you are ready to pop it in the oven. It is recipes like this that I turn to again and again when cooking those big holiday meals.
Table of contents
Ingredient Notes
- Potatoes: A combination of red-skinned sweet potatoes and Yukon Gold potatoes.
- Garlic-infused cream: A combination of half-and-half, butter, and minced garlic.
- Seasoning: All you need is a little salt, freshly ground black pepper, and fresh thyme.
- Cheese: You should be able to find Gruyère cheese in the fine cheese/deli section of your local grocery store and it is so worth it in recipes like this one. It is an excellent melting cheese and it has a rich, nutty, slightly sweet flavor that enhances but does not overwhelm. Paired with the sharp, tangy flavor from the Parmesan, it is out of this world delicious in this gratin.
Methods for Slicing the Potatoes
Mandoline: Using a madoline results in the prettiest, most perfect slices. Set your blade for about 1/8-inch thickness.
Food Processor: When I’m stressed for time, I don’t hesitate to reach for my food processor fitted with the slicing blade. The potato slices won’t be quite as perfect as they mandoline sliced potatoes, but they’ll work just fine.
Knife: You can slice them by hand with a very sharp knife but if they are more than 1/8-inch thick, you will need to increase the baking time a bit to compensate.
How to Make Sweet Potato Gratin
Combine the half-and-half, butter, and garlic in a small saucepan and let it simmer over low heat while you assemble the gratin.
- Arrange half of the potatoes in a greased baking pan, alternating the sweet potato slices with some Yukon Gold potato slices. Sprinkle with half of the salt, pepper to taste, and half of the fresh thyme.
- Sprinkle half of the Gruyère and Parmesan cheese evenly over the top.
- Repeat the layering with the remaining potatoes, salt, pepper, and thyme.
- Top with a final layer of the cheeses, then use your hands to compact the mixture down into the baking dish a bit. Pour the warmed half-and-half mixture over the top, cover and bake in a preheated 400 degree F for 40 minutes. Remove the cover and continue to bake until the top of the gratin is golden, the potatoes are fork tender, and most of the liquid is absorbed.
Tips for the Best Sweet Potato Gratin
Cover before baking: If you’re using a baking dish or pan without a lid, cut off a sheet of foil large enough to cover your dish and coat the bottom side with nonstick cooking spray. This will ensure the cheese will not stick to the foil when you remove it.
Prep-ahead tip: Sliced potatoes have a tendency to turn brown if allowed to sit for too long but you can still get this task out of the way in advance. Just fill a large bowl with cold water and once you slice the potatoes, transfer them to the bowl to soak for up to an hour. When you are ready to proceed with the recipe, transfer the potatoes to a colander to drain, pour them out on to a clean kitchen towel, and pat them dry.
Pretty layering: This first layer will be covered up so save the most even-sized, prettiest slices for the top layer.
Make-ahead tip: This dish can be assembled up to 6 hours ahead of time. Just cover it tightly with plastic wrap and refrigerate. Remove it from the refrigerator about 30 minutes before baking to take the chill off. Remove the plastic wrap and proceed as directed.
Storage and Reheating Tips
Refrigerate: Transfer leftover Sweet Potato Gratin to an airtight container and refrigerate for up to 4 days.
Reheat: Reheat leftovers in the microwave, uncovered, for 2 to 3 minutes, or until warmed through. For larger portions, cover the dish with foil and reheat at 350 degrees F for about 20 minutes, or until warm. If the potatoes seem dry, splash them with a little milk or half-and-half before reheating.
More Potato Side Dish Recipes You’ll Love
- Classic Scalloped Potatoes
- Maple Glazed Sweet Potatoes
- Creamy Au Gratin Potatoes
- Cheesy Make-Ahead Mashed Potatoes
- Sour Cream Mashed Potatoes
- See my entire collection of side dish recipes for more ideas!
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Sweet Potato Gratin
Ingredients
- 1 ½ pounds red-skinned sweet potatoes
- 1 pound Yukon Gold potatoes
- 1 ½ cups half-and-half
- 1 ½ tablespoons butter, divided
- 1 teaspoon minced garlic
- 1 tablespoon chopped fresh thyme
- ½ teaspoon fine ground sea salt, or to taste
- freshly ground black pepper, to taste
- 1 ½ cup shredded Gruyère cheese
- ¼ cup finely shredded Parmesan cheese
Instructions
- Peel the sweet potatoes and Yukon Gold potatoes and use a mandoline or the slicing blade on a food processor to slice them into ⅛-inch thick rounds.
- Combine the half-and-half, 1 tablespoon butter, and garlic in a small saucepan and place over LOW heat. Watch the pot to be sure it doesn’t boil over while you proceed with the rest of the recipe.
- Preheat oven to 400 degrees F. Butter a 12-inch enameled (or regular) cast iron pan (or similar sized gratin dish) with the remaining ½ tablespoon of butter.
- Transfer half of the potatoes to the prepared baking dish, arranging them so that you are alternating the sweet potato slices with some Yukon Gold potato slices. Sprinkle with half of the salt, pepper to taste, and half of the fresh thyme. Sprinkle half of the Gruyère and Parmesan cheese evenly over the top.
- Repeat layering with remaining potatoes, salt, pepper, thyme, and cheeses. Use your hands to compact the mixture down into the baking dish and then pour the half-and-half mixture over the top.
- Cover (*see note below) and bake for 40 minutes. Remove the cover and continue to bake for an additional 15 minutes or until the top of the gratin is golden, the potatoes are fork tender, and most of the liquid is absorbed. Let it rest for 5 to 10 minutes before serving.
Notes
Nutrition
Nutrition information is automatically calculated using generic ingredients, and is an estimate not a guarantee. For more accurate results, please refer to the labels on your ingredients at home.
This post was originally published on October 30, 2018. It has been updated with new text and images.
This dish is now a family favorite and super quick to whip up!!
Great dish but needs finessing. Needs longer baking covered. 10 minutes more. Also could use more liquid. Maybe 1/2 more. Seemed too dry.
Hi, I know this is several years old, but I love this recipe! Do you have any ideas or suggestions on how I could make these as individual servings or small bite size without losing the incredible flavors?
Thank you! I think this will be great with the pork loin I am going to make.
That looks amazing! I am going to try it soon! I have an induction counter top oven, but, I am not sure if it cooks the same. If I make this in the regular oven, would the temps and times be the same?
Hi Beckie! I used the Bake function on the oven so it should be about the same in your conventional oven and it’s pretty fail-proof. Just be sure to let it cook long enough so it’s tender when you remove the foil and you’ll be just fine.