If you’re ready to fall in love with a side dish that perfectly balances creamy, cheesy goodness with the natural sweetness of root vegetables, this Sweet Potatoes Au Gratin Recipe is your new best friend. This dish layers tender, thinly sliced sweet potatoes with a luscious, herb-infused cheese sauce, all baked to bubbling perfection and topped with a delightfully crisp crumb crust. It’s the kind of comforting, festive, and utterly irresistible recipe that you’ll want to bring out for holiday dinners or any time you crave a rich, flavorful twist on a classic gratin.
Ingredients You’ll Need
These simple yet essential ingredients come together to create the magic of this Sweet Potatoes Au Gratin Recipe. Each one plays a special role, whether it’s lending rich creaminess, fragrant herbal notes, or that perfect golden crust that makes every bite delightful.
- 3 lbs. sweet potatoes: Thinly sliced for tender layers that soak up the cheese sauce beautifully.
- 2 tsp. salt (divided): Enhances all the flavors, split to season both potatoes and sauce perfectly.
- ½ tsp. black pepper: Adds a gentle touch of warmth without overpowering the dish.
- 2 Tbsp. butter (salted): The base for a rich, garlicky roux to thicken the sauce.
- 2 Tbsp. flour (all purpose or gluten-free 1-to-1 blend): Creates that silky texture in the cheese sauce.
- 4 cloves garlic (finely minced): Infuses the sauce with aromatic depth and savoriness.
- 1 ½ cups milk (regular or plant-based, room temperature): Blends with the roux for a creamy, smooth sauce that coats every slice.
- 1 cup Gruyere cheese (shredded): Delivers a nutty, slightly sweet cheese flavor that melts perfectly.
- 1 cup cheddar cheese (shredded): Brings a sharp, tangy bite to balance the rich sweetness.
- 1 tsp. each of thyme and rosemary (fresh): Fresh herbs give a fragrant, earthy lift that brightens every forkful.
- ¼ tsp. nutmeg (ground): A subtle hint of spice that adds complexity and warmth.
- 1 Tbsp. butter (melted): Used to bind the crunchy topping together.
- ¼ cup Panko crumbs (or regular breadcrumbs): Provides a golden, crispy texture on top that contrasts beautifully with the creamy layers beneath.
- ¼ cup grated Parmesan cheese: Adds umami richness and a savory finish to the topping.
How to Make Sweet Potatoes Au Gratin Recipe
Step 1: Preheat the Oven
Start by setting your oven to 375 degrees Fahrenheit. This moderate temperature allows the potatoes to cook evenly and the cheese sauce to bubble and thicken without burning, ensuring every slice turns out perfectly tender and golden.
Step 2: Prepare the Potatoes
Begin by washing and scrubbing the sweet potatoes well to remove any dirt. Dry them thoroughly to make slicing easier. Using a mandoline or sharp knife, slice the potatoes into very thin ⅛-inch rounds. The uniform thickness guarantees that your layers will cook consistently and meld together beautifully in the gratin.
Step 3: Layer the Sweet Potatoes
Lightly spray a 13×9-inch baking dish with non-stick spray to keep everything from sticking. Lay half of the sweet potato slices evenly on the bottom, seasoning with half the salt and a bit of black pepper. Add the remaining slices on top and finish seasoning with the rest of the salt and pepper. This seasoning method ensures every layer is flavorful and balanced.
Step 4: Whisk the Cheese Sauce
In a medium saucepan over medium heat, melt 2 tablespoons of butter. Once melted, add the minced garlic and sauté just until fragrant, about 30 to 60 seconds. Lower the heat to medium-low and sprinkle in the flour. Whisk continuously to form a roux—a thick paste that will thicken your sauce. Slowly add the room temperature milk in increments, whisking constantly to keep the sauce smooth and creamy. This gradual process creates the perfect silky base for the cheese blend.
Step 5: Add Cheese and Herbs
Remove the sauce from heat and stir in the shredded Gruyere and cheddar cheeses along with fresh thyme and rosemary. Sprinkle in the nutmeg and remaining teaspoon of salt. Whisk until the cheeses melt completely, turning the sauce into a luscious, velvety topping that will seep into every crevice of your sweet potatoes.
Step 6: Bake Covered
Pour the cheese sauce evenly over the layered potatoes, spreading with a spatula to ensure full coverage. Cover the dish tightly with aluminum foil and bake for 30 minutes. This step allows the potatoes to soften as they absorb the rich flavors under the foil’s gentle, steaming heat.
Step 7: Add the Crispy Crust
While the potatoes bake, combine Panko crumbs, grated Parmesan, and melted butter in a bowl for that final crunchy layer. After the initial baking, remove the foil and sprinkle this topping evenly over the potatoes. Return the dish to the oven uncovered for 15 to 20 minutes until the crust is golden brown and the potatoes are tender when poked with a fork.
How to Serve Sweet Potatoes Au Gratin Recipe
Garnishes
A simple sprinkle of finely chopped fresh rosemary and thyme right before serving brightens the dish, adding fresh herbal notes and a burst of color that makes it feel special and inviting. You can also add a light dusting of extra Parmesan for a cheesy finish.
Side Dishes
This Sweet Potatoes Au Gratin Recipe pairs wonderfully with roasted or grilled meats like chicken, turkey, or pork. The creamy sweetness complements savory mains beautifully, making it an ideal side for holiday dinners or celebratory meals.
Creative Ways to Present
For a party or buffet, try dividing the gratin into individual ramekins before baking. This makes serving a breeze and gives everyone their own personal portion of this irresistible dish. You can also add toasted pecans on top of the crumb crust for an unexpected crunchy twist.
Make Ahead and Storage
Storing Leftovers
Once cooled, cover any leftovers tightly with foil or plastic wrap and refrigerate. The flavors meld beautifully after resting overnight, making for a delicious next-day meal addition.
Freezing
You can freeze portions of the Sweet Potatoes Au Gratin Recipe by placing them in freezer-safe containers or bags. For best results, freeze before baking or immediately after cooling fully to maintain texture. Thaw overnight in the refrigerator before reheating.
Reheating
Reheat leftovers covered in the oven at 350 degrees Fahrenheit until warmed through, about 20 to 25 minutes. This keeps the topping crispy and the potatoes tender, reviving that fresh-baked experience.
FAQs
Can I use regular potatoes instead of sweet potatoes?
Absolutely! Regular potatoes work well in this gratin, though the flavor will be less sweet and more neutral. Yukon Gold or Russets are good choices for a creamy texture.
What can I substitute for Gruyere cheese?
Swiss or Emmental cheeses are great substitutes, as they melt similarly and offer a mild, nutty flavor that complements the cheddar nicely.
Is there a dairy-free version of this recipe?
Yes, use plant-based milk like almond or oat milk and a vegan butter substitute. Also, swap out cheeses with vegan alternatives designed for melting to keep that creamy texture.
How thin should I slice the sweet potatoes?
Slicing the potatoes into ⅛-inch rounds is key to even cooking and getting that perfect tender bite. A mandoline slicer is the easiest tool for consistent thickness.
Can I make this recipe ahead of time?
Definitely! Assemble the dish and refrigerate it before baking. When ready, simply bake as directed, adding extra time if baking from cold.
Final Thoughts
This Sweet Potatoes Au Gratin Recipe is like a warm hug on a plate, bursting with rich, cheesy flavor and the natural sweet brightness of the potatoes. Whether you’re serving it at a festive gathering or craving something comforting on a chilly evening, it’s sure to become a favorite. Dive in, savor every creamy, crunchy bite, and watch it disappear fast at your table!
Print
Sweet Potatoes Au Gratin Recipe
- Prep Time: 25 minutes
- Cook Time: 50 minutes
- Total Time: 1 hour 15 minutes
- Yield: 8 servings
- Category: Side Dish
- Method: Baking
- Cuisine: American
Description
This Sweet Potatoes Au Gratin recipe is a rich, cheesy baked casserole featuring thinly sliced sweet potatoes smothered in a creamy Gruyere and cheddar cheese sauce, enhanced with aromatic herbs and a crispy breadcrumb topping. Perfect as a comforting side dish, it blends the natural sweetness of sweet potatoes with savory, nutty flavors in a warm, golden gratin.
Ingredients
Sweet Potatoes
- 3 lbs. sweet potatoes (cut into ⅛” slices)
- 2 tsp. salt (divided)
- ½ tsp. black pepper
Cheese Sauce
- 2 Tbsp. butter (salted)
- 2 Tbsp. flour (all purpose or gluten-free 1-to-1 blend)
- 4 cloves garlic (finely minced)
- 1 ½ cups milk (regular or plant-based, room temperature)
- 1 cup Gruyere Cheese (shredded)
- 1 cup cheddar Cheese (shredded)
- 1 tsp. fresh thyme
- 1 tsp. fresh rosemary
- ¼ tsp. nutmeg (ground)
- 1 tsp. salt (remaining)
Crumb Topping
- 1 Tbsp. butter (melted)
- ¼ cup Panko crumbs (or regular breadcrumbs)
- ¼ cup grated Parmesan cheese
Instructions
- Preheat the Oven: Preheat your oven to 375 degrees Fahrenheit to get it ready for baking the gratin.
- Prepare the Potatoes: Rinse and scrub the sweet potatoes thoroughly to remove any dirt. Dry them completely using a dish towel. Carefully slice the sweet potatoes into very thin ⅛-inch slices using a mandoline slicer or a sharp chef’s knife to ensure even cooking.
- Layer Potatoes in Baking Dish: Spray a 13×9-inch baking dish with non-stick cooking spray. Arrange half of the sliced sweet potatoes evenly on the bottom of the dish. Sprinkle with ½ teaspoon salt and ¼ teaspoon black pepper. Add the remaining sweet potatoes on top, then season again with ½ teaspoon salt and ¼ teaspoon black pepper for balanced seasoning.
- Make the Cheese Sauce: In a medium saucepan over medium heat, melt 2 tablespoons of butter. Add the minced garlic and sauté for 30 to 60 seconds until fragrant but not browned. Lower the heat to medium-low and sprinkle in the flour. Whisk continuously to form a smooth paste (roux). Gradually add the room temperature milk in ¼ cup increments, whisking well after each addition until the sauce thickens and is smooth.
- Add Cheese and Herbs: Remove the saucepan from the heat. Stir in the shredded Gruyere and cheddar cheeses until fully melted. Then whisk in fresh thyme, rosemary, ground nutmeg, and the remaining teaspoon of salt to infuse rich flavors into the sauce.
- Assemble and Bake Covered: Pour the cheese sauce evenly over the layered sweet potatoes in the baking dish. Use a spatula to spread the sauce so all slices are coated. Cover the dish tightly with aluminum foil and bake in the preheated oven for 30 minutes.
- Prepare and Add Crumb Topping: While the gratin bakes, combine the melted butter, Panko crumbs, and grated Parmesan cheese in a bowl. After 30 minutes, remove the foil from the dish and sprinkle this crumb topping evenly over the potatoes.
- Bake Until Browned and Tender: Return the uncovered dish to the oven and bake for an additional 15 to 20 minutes. This allows the topping to brown nicely and the sweet potatoes to become fork tender.
- Serve: Remove from the oven and serve immediately. Garnish with a sprinkle of finely chopped fresh rosemary and thyme for a fresh herbal aroma and extra flavor.
Notes
- For uniform cooking, slice sweet potatoes very thin (about ⅛ inch thick).
- Use plant-based milk to make this recipe dairy-free, but ensure your cheeses fit your dietary preferences.
- Panko breadcrumbs add extra crunch but regular breadcrumbs work perfectly as well.
- Covering the gratin during the first baking prevents the sauce from drying out.
- This dish can be prepared a day ahead; refrigerate covered and bake as directed before serving.
