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Sweet potato gratin is a wonderful baked and creamy side dish that is so easy to prep. Great Thanksgiving side dish. Made with simple ingredients and perfect to serve with meat, chicken, seafood, and veggie mains.
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I know you will love this delicious sweet potato gratin! Easy to make with a few simple ingredients, it’s a great side to serve up for Thanksgiving and the holidays, but easy enough to make any time of the year.
Layers of sweet potatoes are coated in a garlic and parmesan cream sauce for the most indulgent side that everyone will love!
For more gratin recipes, be sure to check out my Sweet Potato and Kale Gratin and Parmesan Zucchini and Tomato Gratin.
Ingredients for Sweet Potato au Gratin
- Sweet potatoes: Rich in vitamins and minerals including vitamins C, B6, potassium and magnesium.
- Butter: You can use salted or unsalted butter, just adjust the amount of added salt as needed.
- Onion and garlic: To enhance the flavor of the recipe.
- Cream: Use heavy whipping cream for this recipe as it’s nice and thick.
- Arrowroot starch: To thicken the sauce. You can also use cornstarch.
- Lemon juice: Use fresh lemon juice rather than bottled.
- Parmesan cheese: Freshly grated is best, but you can use pre-grated.
- Seasonings: Salt, pepper and rosemary.
How to make sweet potato gratin
- Preheat the oven to 400 F and grease the sides of a baking dish with butter or olive oil.
- Heat butter in a small skillet over medium high heat, add chopped onion, and saute until tender and translucent, about 2-3 minutes. Add minced garlic, and cook for 30 seconds until fragrant. Pour heavy whipping cream and stir. In a small bowl, make a slurry of the warm heavy cream and arrowroot starch. Add back to the skillet and stir well until sauce thickens. Turn off the heat and set aside.
- Place sliced sweet potatoes overlapping each other in one layer in the baking dish. Season with salt, pepper, and rosemary. Pour half of the onion mixture, and sprinkle ½ cup of the parmesan cheese on top.
- Place another layer of overlapping sweet potato slices on top. Season them with salt, pepper, and rosemary. Pour remaining onion mixture, and sprinkle remaining Parmesan cheese on top.
- Bake in a preheated oven for 30 – 40 minutes until the sweet potatoes are tender and cooked through. Let the sweet potato gratin cool for 5 – 10 minutes, and serve warm. The sauce will thicken as it cools.
What is a gratin?
A gratin is a creamy French dish that is baked in the oven and topped with cheese, and sometimes breadcrumbs. Often made with layered potatoes, other veggies can be used too.
Can you make it ahead of time?
This is a great make ahead dish, so it’s a good option if you are planning a big feast.
You can assemble the whole dish the day before and keep it covered in the fridge. Just bake the scalloped sweet potatoes when you are ready to serve.
You can also cook the creamy sweet potato bake up to 3 or 4 days ahead of time and it will keep well in the fridge. Reheat the dish, covered with foil at 350F until heated through.
Can you freeze it?
Yes, this sweet potato au gratin is a great freezer side, and you can freeze it baked or unbaked. Freeze it in the dish and securely wrap it with foil and place it in a freezer bag. Thaw in the fridge overnight before cooking or reheating.
Recipe Notes and tips
- Slice the sweet potato evenly so that everything cooks through. A mandolin is the easiest and quickest way to do this.
- If needed, you can brown the top of the sweet potato gratin under the broiler once it has baked.
- The sweet potatoes should be fork tender once baked.
- To make this vegetarian, use parmesan cheese without rennet.
More Sweet Potato Recipes
- Sweet Potato Fries with Paprika Garlic Aioli
- Baked Sweet Potato Slices
- Sweet Potato Sausage Frittata
- Baked Sweet Potato Chips
Sweet Potato Gratin
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Ingredients
- 1.5 lbs sweet potatoes, about 2 -3 sweet potatoes, sliced thinly on a mandoline (⅛”)
- 3 Tablespoon butter
- ½ cup onion, finely chopped
- 3 – 4 garlic cloves, finely minced
- 1 cup heavy whipping cream
- 1 Tablespoon arrowroot starch, (or cornstarch)
- Juice of ½ lemon
- 1 cup parmesan cheese, thinly grated
- Salt and pepper, to taste
- 1 teaspoon rosemary
Instructions
- Preheat the oven to 400 F and grease the sides of a baking dish with butter or olive oil.
- Heat butter in a small skillet over medium high heat, add chopped onion, and saute until tender and translucent, about 2-3 minutes. Add minced garlic, and cook for 30 seconds until fragrant. Pour heavy whipping cream and stir. In a small bowl, make a slurry of the warm heavy cream and arrowroot starch. Add back to the skillet and stir well until sauce thickens. Turn off the heat and set aside.
- Place sliced sweet potatoes overlapping each other in one layer in the baking dish. Season with salt, pepper, and rosemary. Pour half of the onion mixture, and sprinkle ½ cup of the parmesan cheese on top.
- Place another layer of overlapping sweet potato slices on top. Season them with salt, pepper, and rosemary. Pour remaining onion mixture, and sprinkle remaining Parmesan cheese on top.
- Bake in a preheated oven for 30 – 40 minutes until the sweet potatoes are tender and cooked through. Let the sweet potato gratin cool for 5 – 10 minutes, and serve warm. The sauce will thicken as it cools.
Video
Notes
- Slice the sweet potato evenly so that everything cooks through. A mandolin is the easiest and quickest way to do this.
- If needed, you can brown the top of the gratin under the broiler once it has baked.
- The sweet potatoes should be fork tender once baked.
- To make this vegetarian, use a parmesan cheese without rennet.
I am going to try this today but not seeing in the instructions where you add the lemon juice ???