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This Sweet Potato Gratin is everything you want in a cozy fall or holiday side dish. Layers of tender sweet potatoes are baked in an herbed cream sauce with fresh sage, thyme, garlic, and just the right amount of Parmesan. It’s elegant enough for your Thanksgiving table and easy enough for a weeknight dinner.
If you’re planning your holiday menu, pair it with Roast Turkey Breast (with herb butter), Green Bean Casserole, and Homemade Stuffing for a complete meal.
5 Things That Really Matter in Sweet Potato Gratin
- Slice evenly: Use a mandoline for consistent ⅛-inch slices so everything cooks evenly.
- Avoid watery results: Dry the sweet potato slices before layering and bake uncovered for proper evaporation.
- Layer with purpose: Even, overlapping layers help the gratin hold together and cook through.
- Check doneness: A paring knife should glide through easily. If not, add time to avoid undercooked spots.
- Let it rest: Resting after baking helps the cream set and the layers stay intact when serving.
RECIPE WALK-THROUGH
How To Make Sweet Potato Au Gratin
See the recipe card below for full, detailed instructions
The balance of sweet and savory, creamy and cheesy, is what makes this gratin a standout. The herbed cream infuses every slice, and the thin, even layers ensure perfectly tender results every time.
Step 1: Prep and preheat
Preheat oven to 350°F. Lightly grease a 2.5 or 3-quart baking dish with nonstick spray.
Step 2: Make the cream mixture
In a measuring cup or bowl, combine 1½ cups heavy cream, five minced garlic cloves, one tablespoon chopped fresh sage, ½ teaspoon dried thyme, two teaspoons kosher salt, and ½ teaspoon black pepper. Mix well.
- Freshly minced garlic provides the best flavor! “Jarlic” is better than no garlic, but fresh garlic cloves are ideal.
Step 3: Layer the gratin
Peel and thinly slice five large sweet potatoes (about 2.5 lbs) into ⅛-inch-thick slices. Lay down ¼ of the sweet potato slices in overlapping circles. Pour over ¼ of the cream mixture, then sprinkle with two tablespoons of Parmesan cheese.
Repeat this process to create four total layers, ending with cream and cheese. Spoon out the remaining herbs and garlic from the bottom of the bowl for the final layer.
- A mandolin is a great option for slicing potatoes! Just be careful and use the guard.
Step 4: Bake
Bake uncovered for 40-45 minutes. Test the center with a paring knife. If the potatoes aren’t fully tender, bake another 10-15 minutes. The dish is done when the knife goes in easily and the top is lightly golden brown.
- If the top browns before the potatoes are tender, cover with foil for the final portion of the cook.
Step 5: Rest and serve
Remove from oven and let sit for 10 minutes before serving. Garnish with extra Parmesan and chopped fresh sage.
More Sweet Potato Recipes To Try
- Brown Sugar & Bacon Mashed Sweet Potatoes – This is decadent and delicious. Perfect if you want something a little over-the-top.
- Sweet Potato Casserole Recipe – A go-to recipe for the holidays, complete with the marshmallow topping.
- Sweet Potato Dip – You’ve never had a dip like this before. This is an incredible appetizer!
- Sweet Potato Wedges – Crispy, simple, and a great alternative to traditional potato wedges.
Variations
- Lighter Gratin: Use half-and-half instead of heavy cream for a slightly lighter version.
- Gruyere Sweet Potato Gratin: Swap half the Parmesan for shredded Gruyere for a nuttier, more robust flavor.
- Add Cheese: Parmesan, Gruyere, or Fontina make great toppings.
- Herbs: Thyme, sage, rosemary, or chives add color and flavor.
- Crunch Factor: Add some buttered breadcrumbs or crushed pecans on top!
- Flavor Boost: Caramelized onions or a drizzle of browned butter before baking add a ton of flavor.
Serving Suggestions
Serve alongside roast turkey, glazed ham, or herb-roasted chicken. Add a crisp green salad or roasted Brussels sprouts for balance.
Storage Tips
Storage, Freezing, Make Ahead
- Fridge – Wrap leftovers tightly and store for up to 3 days.
- Reheat – Warm uncovered in a 325–350°F oven until heated through.
- Freeze – Not ideal, as the cream can separate, but doable. Cool completely, wrap well, and freeze for up to 1 month. Thaw overnight before reheating.
- Make-Ahead Tip – Assemble up to 1 day ahead and refrigerate before baking. Let it come to room temperature and bake as directed.
Frequently Asked Questions
Can I make sweet potato gratin without cream?
Yes, you can use half-and-half or even whole milk, but the result will be lighter and slightly less rich. Consider thickening the milk with a roux (butter + flour) if skipping cream.
What’s the best cheese to use?
Parmesan adds salty richness, but Gruyere, cheddar, or Fontina also work well.
Why is my gratin watery?
Too much liquid or underbaking can cause this. Make sure to bake uncovered so excess moisture evaporates, and allow it to rest to help the sauce thicken.
Can I use a food processor to slice the potatoes?
Yes! Use the slicing attachment to quickly get thin, even rounds.
More Holiday Recipes
- Cheesy Scalloped Potatoes
- Mashed Sweet Potatoes
- Green Bean Casserole (from scratch)
- Oven Roasted Turkey Breast
- Crispy Garlic Roasted Potatoes
Sweet Potato Gratin
Ingredients
- 5 large Sweet potatoes (about 2.5lbs), peeled and sliced ⅛” thick
- 1 ½ cups Heavy cream
- 5 cloves Garlic minced
- 1 tablespoon Fresh sage chopped, plus more for garnish
- ½ teaspoon Dried thyme leaves
- 2 teaspoon Kosher salt
- ½ teaspoon Black pepper
- ½ cup Freshly grated parmesan cheese divided
Instructions
- Preheat the oven to 350 degrees. Grease the bottom and sides of a 2.5-3 quart baking dish with non-stick cooking spray and set aside.
- In a measuring cup mix the heavy cream, garlic, sage, thyme, salt and pepper together well. Set aside.
- Place ¼ of the sweet potatoes into the baking dish overlapping each other working clockwise then down the center. Pour ¼ of the cream mix over the sweet potatoes and sprinkle with 2 tablespoons of the Parmesan cheese.
- Continue layering with remaining potatoes, cream and cheese to have 4 layers total. On the final layer make sure to spoon out the settled seasoning/garlic from the cream sauce.
- Bake uncovered 350 degrees for 40-45 minutes. Using a paring knife, press into the center; if the potatoes give resistance, continue cooking for an additional 15 minutes which will also help brown the top.
- Let the gratin sit for about 10 minutes, garnish with more sage and grated parmesan cheese if desired and serve.
Notes
- Slice sweet potatoes evenly for even cooking.
- Tent with foil if browning too quickly.
- Let the baked gratin rest before slicing.
- Use gruyere or cheddar for a richer flavor.
- Make ahead: assemble up to 1 day ahead and refrigerate before baking. Let it come to room temperature and bake as directed.
- Store leftovers in the fridge up to 3 days.
- Reheat uncovered at 325°F.
Nutrition
Nutritional Disclaimer Kristin Maxwell of “Yellow Bliss Road” is not a dietician or nutritionist, and any nutritional information shared is an estimate. For accurate calorie counts and other nutritional values, we recommend running the ingredients through your preferred online nutritional calculator. Calories and other nutritional values can vary depending on which brands were used.
