Creamy, Cheesy Sweet Potato Gratin (video)

30 prep + 1 cook

servings

The best sweet potato side dish for the holidays! Sweet potato gratin is made with thinly sliced potatoes baked in a cheesy béchamel sauce!

Begin with the sauce. Preheat a large sauté pan over medium heat and melt the butter in the pan. Add in the diced shallots and cook for 4 to 5 minutes, until the shallots are tender and translucent; don’t brown. Next, add in the garlic, thyme, and rosemary and cook for about 30 seconds.
Sprinkle in the flour, toss until it’s absorbed into the butter, then cook for 1 minute. Beginning adding the milk, about ½ cup at a time. Whisk after each addition and cook until the sauce thickens before adding the next portion. Pour in the cream last.
Season the sauce with salt, pepper, and a touch of freshly ground nutmeg. Allow the sauce to come up to a simmer over medium heat. Add 1 cup of parmesan cheese and 1 cup of gruyere cheese and cook just until the cheese is dissolved, about 1 minute.
Cover the sauce with a lid, remove from the heat and keep it warm on the side.

Peel the sweet potatoes, then rinse them with cold water to keep them from browning.
Using a sharp, large knife or a mandolin slicer (my preferred method), slice the potatoes to 1/8-inch thickness. Make sure to use a cut glove whenever you use a slicer!
Keep the sliced potatoes in neat stacks on a separate tray. This will make the assembly much easier and quicker.

Preparing an oven-safe casserole pan for baking the sweet potato gratin. Line the inside of a large oval, square or round pan with Reynolds Wrap® Heavy Duty Foil. If needed, use two overlapping sheets to ensure the sauce doesn’t leak.
Pour half of the prepared béchamel sauce into your lined casserole dish. Work with 10 to 15 slices of sweet potato at a time. Stack the potatoes neatly, then fan them slightly before arranging them into the pan.
Watch my video tutorial to see how I arranged mine. Tuck any smaller pieces and ends of the sweet potatoes into the sides.
Spoon the remaining sauce over the arranged sweet potatoes, ensuring they’re well covered. Cover the casserole dish tightly with another sheet of Reynolds Wrap® Heavy Duty Foil.

Bake the gratin in a preheated oven set to 350°F for 1 to 1 and 15 minutes, until the sweet potatoes are cooked and very tender. Check for doneness using a knife or toothpick.
Remove the foil from the top and sprinkle the remaining ½ cup parmesan and ½ cup gruyere cheese on top. Switch the oven setting to broil, and broil on the ‘high’ setting for 5 to 8 minutes, until the cheese is melted and lightly browned.
This creamy, cheese sweet potato gratin will be extremely hot coming out of the oven! Allow it to cool for about 30 minutes before enjoying. I love to serve it with roasted chicken, turkey, lamb chops, duck, or even ham. It’s a fantastic side dish for all your holiday main dishes!