Twice-Baked Sweet Potato Gratin
Inside: Fluffy mashed sweet potatoes with rosemary, black pepper and Gruyère, baked in individual ramekins under a browned cheese cap. Make-ahead instructions, a casserole-dish version, and how to use leftover baked sweet potatoes.
For the longest time, I didn’t like sweet potatoes. I bypassed them at the market and snubbed them on restaurant menus, and I blame the marshmallow-topped casseroles that turned every holiday side into dessert. These twice-baked sweet potato gratins changed my mind. The sweet potatoes get baked, scooped and whipped with butter, rosemary and a heavy hand of nutty Gruyère, then packed into ramekins and baked again until the cheese on top is golden and bubbly. Everyone gets their own. And since you can fill the ramekins a day ahead, they’re ready to slide into the oven while the turkey rests.
Why you’ll love these:
- Savory, not sugary. Rosemary, black pepper and Gruyère do the work brown sugar and marshmallows usually do. The sweet potato’s natural sweetness is plenty.
- Built-in portion control. Individual ramekins look like you went to a lot of trouble. You didn’t.
- Make-ahead friendly. Assemble, refrigerate, then bake and broil right before dinner.
- A second life for leftovers. Already have baked or mashed sweet potatoes? You’ve skipped the longest step.
Ingredients for Twice-Baked Sweet Potato Gratin
- Sweet potatoes: About 1½ pounds, which is 2 to 3 medium. Pick potatoes similar in size so they finish baking at the same time. The orange-fleshed ones labeled “yams” at most U.S. grocery stores work the same.
- Gruyère: Nutty, a little salty, and it melts smoothly without going greasy. Shred it yourself; bagged pre-shredded cheese has anti-caking starch that keeps it from melting cleanly.
- Fresh rosemary: Chop it fine. Rosemary is assertive, and a teaspoon is enough to perfume six ramekins.
- Milk and butter: A modest amount of each. The cheese brings the richness, so this gratin has no cream.
- Kosher salt and freshly ground black pepper: The pepper is a flavor, not an afterthought. Grind it fresh.
How to Make Twice-Baked Sweet Potato Gratin
1. Bake the sweet potatoes. Line a sheet pan with foil (sweet potatoes drip sugary juice that burns onto the pan) and bake until a paring knife slides through the thickest part with zero resistance. That can take 45 minutes to well over an hour depending on size, so go by the knife, not the clock. [Image: baked sweet potatoes. Caption: “Bake until a knife slides through with no resistance.”]
2. Scoop the flesh. Halve the potatoes, let them cool enough to handle, and scoop the flesh into a bowl. Toss the skins.
3. Mash until smooth. A potato ricer gives the silkiest texture. A hand mixer works too.
4. Season. Stir in the rosemary, salt and pepper, then the milk and butter.
5. Add most of the cheese. Fold in all but ¼ cup of the Gruyère. Taste here and adjust the salt.
6. Fill the ramekins. Divide the mixture among six greased ½-cup ramekins, smooth the tops, and sprinkle with the remaining cheese. This is your make-ahead stopping point.
7. Bake, then broil. Bake at 350°F until hot through, then broil for 2 to 3 minutes until the cheese is browned in spots. Watch them under the broiler; Gruyère goes from golden to burnt fast.
Pro-Tips:
- Trust the knife test. Undercooked sweet potatoes won’t mash smooth, and you’ll be chasing lumps forever. If yours are large, bake at 400°F instead of 375°F.
- Let the scooped flesh steam for a few minutes before mashing. Some excess moisture evaporates, and the filling holds its shape better in the ramekins.
- Set the ramekins on a sheet pan for the second bake. This makes it easier to move in and out of the oven, and no cheese will weld to your oven floor.
- Stand by the broiler. Two minutes is usually enough. Three can be too many.
Mistakes To Avoid:
- Pulling the potatoes too early. This is the number-one issue readers have run into. Firm spots mean a lumpy, uneven filling.
- Using a food processor or blender. Overworking the flesh turns it gluey. A ricer, masher or hand mixer is all you need.
- Pre-shredded cheese. It melts grainy. Buy a wedge of Gruyère and shred it.
- Skipping the broil. The browned cheese cap is the whole point of a gratin.
Swaps and Variations:
- Cheese: Comté is Gruyère’s closest cousin. Fontina, Swiss or a sharp white cheddar also work.
- Herbs: Swap the rosemary for fresh thyme or a few chopped sage leaves.
- Richer: Use half-and-half or cream instead of milk.
- Crunch: Toss a few tablespoons of panko with melted butter and scatter it over the cheese before baking.
- Add-ins: Crumbled crisp bacon, caramelized onions, or a few cloves of mashed black garlic for a deep, molasses-y sweetness from the Maillard reaction.
- One big casserole: Spread the mixture into a small greased baking dish instead of ramekins and bake 25 to 30 minutes before broiling.
Make ahead:
- Fill the ramekins, top with cheese, cover with plastic wrap and refrigerate up to 2 days.
- Let them sit on the counter while the oven heats, then bake and broil as directed.
- Straight from the fridge, they’ll need about 20 to 25 minutes instead of 15 to heat through.
Storage:
- Cover and refrigerate baked ramekins up to 4 days. Reheat at 350°F until hot, about 15 minutes, or microwave in 30-second bursts.
Reheating:
- Reheat at 350°F until hot, about 15 minutes.
- Or Microwave in 30-second bursts.
Freezing:
- Wrap the filled, unbaked ramekins tightly and freeze up to 3 months. Thaw overnight in the fridge before baking.
Twice-Baked Sweet Potato Gratin FAQs
Yes, and that’s exactly what this recipe is. Six ½-cup ramekins hold one batch. Individual portions bake faster than a full casserole, and every serving gets its own browned cheese top.
Yes. Spread the filling in a small greased baking dish, top with the remaining cheese, and bake at 350°F for 25 to 30 minutes, then broil until browned.
This. If you have plain leftover baked sweet potatoes, scoop the flesh and start at step 3. If you have leftover mashed sweet potatoes, warm them slightly so they’re easier to stir, then fold in the rosemary, cheese and seasoning. If your leftover mash already has butter and milk in it, hold back some of the butter and milk here.
A paring knife should slide into the thickest part with no resistance. If you’re using a thermometer, look for around 205°F in the center. Size matters more than time; large sweet potatoes can take well over an hour.
This one has no cream. A little milk and butter keep the mash smooth, and the Gruyère does the heavy lifting on richness.
At most U.S. grocery stores, the orange-fleshed “yams” are actually sweet potatoes, and they work the same here. True yams are a different, starchier tuber you’re more likely to find at international markets. I’d skip canned yams for this recipe; they’re packed in syrup and too sweet and wet for a savory gratin.
Same idea, different shape. Traditional twice-baked sweet potatoes get stuffed back into their skins. I’ve tried this, and it’s harder than you’d think; the skins tear more easily than a traditional baking potato. Here the filling goes into ramekins, which means less fiddly work, a better cheese-to-potato ratio, and nothing to tear.
What to serve with Twice-Baked Sweet Potato Gratin:
These hold their own next to anything roasted. They’re a natural fit for the holiday table, and they’re every bit as good on a weeknight next to pork chops with pan gravy or an herb-crusted pork loin. Round out the plate with holiday green beans or Brussels sprouts with bacon and maple.
Feeding a crowd and want one big dish instead of ramekins? My savory sweet potato casserole layers sliced sweet potatoes with bacon, apples and an herb custard. Prefer them smooth and classic? Go with creamy whipped sweet potatoes.
More casserole and gratin side dishes you’ll love:
- Savory Sweet Potato Casserole
- Creamy Scalloped Potatoes with Thyme
- Cheesy Rutabaga Butternut Squash Casserole
- Kale Barley & Mushroom Gratin
- Mashed Cauliflower with Roasted Garlic
- Chayote Gratin
- Leftover Mashed Potato Souffle
- Butternut Squash Puree
- Cauliflower and Mushroom Gratin
- Cheesy Tomato Egg Gratin
Twice-Baked Sweet Potato Gratin
INGREDIENTS:
- 1 ½ pounds sweet potatoes
- 1 teaspoon rosemary chopped fresh
- ½ teaspoon kosher salt
- ¼ teaspoon black pepper freshly ground
- ¼ cup milk
- 1 tablespoon butter
- 1 ½ cups gruyere cheese shredded, divided
DIRECTIONS:
- Preheat the oven to 375 degrees.
- Place the potatoes on a baking sheet lined with aluminum foil and Bake at 375°F (or 400°F for large potatoes) for 45 to 75 minutes, until a knife slides through the thickest part with no resistance. Remove from the oven and cut each potato in half. Let the potatoes cool until you can handle them, then scoop out the flesh into a bowl.
- Use a potato ricer or hand mixer to puree the potatoes. Stir in the rosemary, salt and pepper. Add the milk and butter and stir until butter has melted. Add 1 1/4 cups of gruyere and stir to combine. Set aside.
- Spray 6 half-cup ramekins with vegetable spray. Divide the sweet potatoes among the ramekins and smooth the tops with the back of a spoon. Sprinkle with the remaining cheese.
- Can be made in advance to this point and refrigerated until ready to bake.
- To bake the gratins, preheat the oven to 350°. Place the gratins on a baking sheet and bake for 15 minutes until warmed through then turn on the broiler and cook for an additional 2-3 minutes until lightly browned. Serve.
NOTES:
- Make ahead: Fill ramekins, cover and refrigerate up to [2 days]. Add [5 to 10] minutes to the bake time if baking straight from the fridge.
- Casserole dish: Bake in a small greased dish for 25 to 30 minutes, then broil.
- Leftovers: Already have baked sweet potatoes? Start at step 3.
NUTRITION:
Nutritional Disclaimer
Nutritional information is an estimate only and is provided as a courtesy. Values are calculated automatically based on the ingredients and quantities in each recipe and may vary depending on specific brands, exact measurements, and substitutions made. For precise nutritional guidance, especially if you have a medical condition or dietary restriction, please consult a registered dietitian or run the ingredients through your own nutrition calculator.Don’t Forget To “Pin It” For Later!
Plan to make this but the recipe says it serves 6 and the # of ramekins filled as per the instructions is 4. Which is it?
Sorry about that — I did fix it in the recipe. It makes 6.
Sounds great. Wish I could email it to myself since can’t print from phone. Could send to friend too. I get the icon to d o so but doesn’t work.
I sent you the link!
I found that over an hour at 375 was not long enough to cook the sweet potato. Any idea why?
It could be the size of your sweet potatoes… You can increase the temperature to 400° for 45 minutes to an hour, but cooking is a tactile experience… I generally “test” the doneness by sticking the potatoes with a knife. If it inserts and exits easily, its done.
Have you baked this in a casserole dish? If so how long does it bake
I bake them in individual ramekins, but you could put them in a casserole. I’d let them cook for 25-30 minutes or until golden and bubbly.
Anything it’s Potatoes gets a big thumbs up from me. This looks so comforting and perfect for autumn.
I’ve never seen a gratin done in this way or with sweet potatoes… i am loving the sound of your recipe!! I definitely need to give this one a try! Thanks!
This looks like the perfect addition to my Thanksgiving table, can’t wait to try it!
I love sweet potatoes and could eat them all the time! This is an awesome recipe and I can’t wait to make it. I never thought of making it as an au gratin! Perfect!
Okay, I am SUPER intrigued now because I have always been the same about sweet potatoes! But now I’m thinking about savory ones and the flavors here and I think you might have just converted me!
If there’s an “ick factor” to marshmallow topped sweet potatoes, this is the cure.
Thank you so much for this fantastic recipe, your delicious sweet potatoes accompanied our dinner last night and was a huge hit with my entire family.
Kerryanne, thank you so much for letting me know! I’m glad that you and your family enjoyed them! They are special!
Hello! I hope you’re having a good week. Your sweet potato recipe looked so tasty (seriously tasty – it’s on my shortlist of things to make) that I?ve linked to it my latest post on BuzzFeed.
Thanks for including me and I’m so glad you liked this recipe. I think anything with gruyere is good!
I can’t argue with that. Give me all the cheese. 🙂