Sweet Potato Gratin
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This Sweet Potato Gratin combines thinly sliced sweet potatoes with Gruyère, Fontina, Parmigiano-Reggiano, fresh thyme, and a touch of smoked paprika. The potatoes bake in heavy cream until tender and bubbling, then finish with a deeply golden layer of cheese and a hint of fresh orange zest. This savory side dish is especially delicious for Thanksgiving, Christmas, and other fall and winter meals.
If you love this recipe, you should try my Savory Sweet Potato Casserole, Candied Sweet Potatoes, and Vegetable Au Gratin Recipe.
Quick Look: Sweet Potato Gratin
- Servings: 10 people
- Prep Time: 20 minutes
- Cook Time: 1 hour 30 minutes
- Resting Time: 15 minutes
- Total Time: 1 hour 50 minutes
- Course: Side Dish
- Cuisine: American, Italian-Inspired
- Method: Baking
- Dietary Info: Vegetarian, Gluten-Free
- Technique: Slice the sweet potatoes into thin, even rounds, season them with herbs and spices, arrange them upright in a baking dish with cheese between the layers, then bake with heavy cream before finishing with more cheese until deeply golden and tender.
- Flavor & Texture: Creamy, savory, cheesy, delicately sweet, golden
Why You’ll Love This Holiday Sweet Potato Recipe!
In my family, sweet potatoes are usually served simply roasted, so when I make them for a special holiday meal, I still want their natural flavor to shine. This cheesy sweet potato gratin feels indulgent and festive, but it isn’t sugary or overly sweet (we have dessert for that!).
The beautiful circular arrangement makes this company-worthy, yet the method is straightforward. Slice, season, arrange, pour, and bake. That is my kind of impressive holiday recipe!
Great side for Roasted Thanksgiving Turkey, Baked Ham Recipe (With Glaze), Porchetta Recipe, and Beef Tenderloin Roast.
Made With Amore,
Table of Contents
Simple Ingredients
Sweet potatoes au gratin requires only a few basic, fresh ingredients to make a showstopping dish!
- Sweet Potatoes: Orange-fleshed sweet potatoes become tender and creamy while their natural sweetness balances the savory seasonings and cheese.
- Gruyère, Fontina, And Parmigiano-Reggiano: Gruyère adds nutty flavor, Fontina creates a creamy melt, and Parmigiano-Reggiano brings savory depth and a golden finish.
- Heavy Cream: Bakes between the potato slices to create the creamy base.
- Fresh Thyme and Orange Zest: Thyme adds an earthy herbal note, while optional orange zest brings a subtle brightness to the rich ingredients.
- Smoked Paprika and Garlic Powder: Add savory depth and a light smoky flavor that complements the natural sweetness of the potatoes.
See recipe card for full information on ingredients and quantities.
Variations & Substitutions
- Potatoes: Yukon Gold or russet potatoes can be used in place of sweet potatoes. Try this version with Yukon Gold potatoes: Homemade Au Gratin Potatoes, or my Vegetable Au Gratin Recipe.
- Lighter Version: Replace 1 cup of the heavy cream with whole milk. The sauce will be lighter and slightly less thick but still creamy.
- Cheese: Gruyère, Fontina, and Parmigiano-Reggiano create the signature flavor and texture, but you can substitute another good melting cheese if needed. If Gruyère is unavailable, use Comté or aged white cheddar. Provolone or low-moisture mozzarella can replace the fontina. You’ll also love this Creamy Cheesy Cauliflower Casserole.
How to Make Sweet Potato Gratin
This sweet potato gratin comes together with thinly sliced potatoes, layers of cheese, seasoned cream, and a golden finish from the oven. Follow the step-by step photos and see the recipe card at the bottom for a printable version.
- Preheat the oven to 375°F. Lightly grease a baking dish with extra-virgin olive oil. Using a mandoline or a sharp knife, slice the peeled sweet potatoes into uniformly thin, approximately ⅛-inch rounds. Do not rinse or soak the slices; their natural starch helps the cream thicken as the gratin bakes.
- Place the sliced sweet potatoes in a large bowl. Add 1 tablespoon of olive oil, salt, black pepper, nutmeg, smoked paprika, garlic powder, chopped thyme, and orange zest, if using. Gently toss with your hands until the slices are evenly coated and seasoned.
- Mix the Gruyère, fontina, and Parmigiano in a separate bowl. Set aside approximately 1 cup of the cheese mixture for the final topping. Begin around the outside edge of the baking dish and arrange the sweet potato slices upright at a slight angle, overlapping each slice by about one-third. Tuck small amounts of the remaining cheese between the rows as you work. Continue working in tight circles toward the center.
- Slowly pour the heavy cream evenly over the arranged sweet potatoes. Press the potatoes down gently so the cream settles between the slices. The potatoes do not need to be completely submerged. Cover the baking dish tightly with aluminum foil. Bake for 30 minutes. Remove the foil and bake for another 30 minutes. The cream should be bubbling around the edges, and the potatoes should be starting to soften.
- Sprinkle the reserved cheese evenly over the top. Bake uncovered for approximately 25 minutes more, until the top is deeply golden and a thin knife slides easily through the center of the potatoes.
- Remove the gratin from the oven and let it rest uncovered for at least 15 minutes. The cream will continue to thicken as it rests. Garnish with fresh thyme and serve warm.
Sweet Potato Gratin FAQs
The terms are often used interchangeably, but traditionally, au gratin potatoes include cheese. Scalloped potatoes are typically baked in cream or a white sauce and may not contain cheese.
No. There is no need to rinse or soak the sweet potatoes after slicing. Their natural starch helps the cream thicken as the gratin bakes.
The gratin may need more baking time uncovered, or it may not have rested long enough. Other causes include adding too much liquid, rinsing away the potato starch, using a watery cheese, or slicing the potatoes too thickly.
Make Ahead: Bake the gratin up to one day ahead, cool, cover, and refrigerate. Reheat covered at 350°F for 20–30 minutes, then uncover for the final 5 minutes. For best results, do not assemble it raw in advance.
Storage and Reheating: Store covered in the refrigerator for up to 4 days. Reheat at 350°F until warm or microwave individual servings. Freezing is not recommended since the cream sauce may separate.
Serving Suggestions
I love serving this sweet potato gratin alongside roasted meats and other vegetable dishes, especially for a holiday meal. Try it as a side with Roast Turkey Breast or Juicy Oven Roasted Chicken. For additional sides, I like to make Homemade Dinner Rolls, a fresh Shaved Brussels Sprouts Salad, and Roasted Green Beans. The creamy, cheesy potatoes pair especially well with simply seasoned meats and fresh green vegetables.
My Pro Tips
Recipe Tips
- Slice the potatoes no thicker than ⅛ inch. Thick or uneven slices are the most common reason a gratin takes too long to become tender.
- Test the center, not just the edges. A knife should pass through the middle without resistance.
- Baking dishes vary in depth. A deeper dish may require an additional 10–15 minutes.
- Freshly grated cheese melts more smoothly than packaged shredded cheese, which often contains anti-caking ingredients.
- Allow the gratin to rest for the full 15 minutes. This is when the bubbling cream settles into a rich, spoonable sauce.
More Holiday Side Recipes You’ll Love
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Sweet Potato Gratin
Ingredients
- 3 pounds sweet potatoes, orange-fleshed, peeled
- 1 tablespoon extra-virgin olive oil, plus more for greasing the baking dish
- 1 teaspoon kosher salt
- ½ teaspoon freshly ground black pepper
- ½ teaspoon ground nutmeg
- ½ teaspoon smoked paprika
- 1 teaspoon garlic powder
- 5 –6 sprigs fresh thyme, leaves removed and finely chopped, plus more for garnish
- 1 tablespoon finely grated fresh orange zest, optional
- 1 cup freshly grated Gruyère cheese
- 1 cup freshly grated fontina cheese
- ½ cup freshly grated Parmigiano-Reggiano cheese
- 2 cups heavy cream
Instructions
- Prepare the oven and baking dish. Preheat the oven to 375°F. Lightly grease a 3-quart round or oval baking dish with extra-virgin olive oil.
- Slice the sweet potatoes. Using a mandoline or a sharp knife, slice the peeled sweet potatoes into uniformly thin, approximately ⅛-inch rounds. Do not rinse or soak the slices; their natural starch helps the cream thicken as the gratin bakes.
- Season the potatoes. Place the sliced sweet potatoes in a large bowl. Add 1 tablespoon olive oil, salt, black pepper, nutmeg, smoked paprika, garlic powder, chopped thyme, and orange zest, if using. Gently toss with your hands until the slices are evenly coated and seasoned.
- Combine the cheeses. Mix the Gruyère, fontina, and Parmigiano in a separate bowl. Set aside approximately 1 cup of the cheese mixture for the final topping.
- Arrange the sweet potatoes. Begin around the outside edge of the baking dish and arrange the sweet potato slices upright at a slight angle, overlapping each slice by about one-third. Tuck small amounts of the remaining cheese between the rows as you work. Continue working in tight circles toward the center.
- Add the cream. Slowly pour the heavy cream evenly over the arranged sweet potatoes. Press the potatoes down gently so the cream settles between the slices. The potatoes do not need to be completely submerged.
- Cover and begin baking. Cover the baking dish tightly with aluminum foil. Bake for 30 minutes.
- Continue baking uncovered. Remove the foil and bake for another 30 minutes. The cream should be bubbling around the edges, and the potatoes should be starting to soften.
- Add the final cheese layer and bake more. Sprinkle the reserved cheese evenly over the top. Bake uncovered for approximately 25 minutes more, until the top is deeply golden and a thin knife slides easily through the center of the potatoes.
- Rest before serving. Remove the gratin from the oven and let it rest uncovered for at least 15 minutes. The cream will continue to thicken as it rests. Garnish with fresh thyme and serve warm.
Notes
- Slice the potatoes no thicker than ⅛ inch. Thick or uneven slices are the most common reason a gratin takes too long to become tender.
- Test the center, not just the edges. A knife should pass through the middle without resistance.
- Baking dishes vary in depth. A deeper dish may require an additional 10–15 minutes.
- Freshly grated cheese melts more smoothly than packaged shredded cheese, which often contains anti-caking ingredients.
- Allow the gratin to rest for the full 15 minutes. This is when the bubbling cream settles into a rich, spoonable sauce.
Nutrition
Nutrition information is automatically calculated, so should only be used as an approximation.
