Homemade Sweet Potato Au Gratin

Homemade Sweet Potato Au Gratin is the creamy, cheesy, comfort food dish that you didn’t know you needed. Layers of sweet potatoes with a creamy sauce, garlic, thyme, sage, Romano cheese and a pinch of nutmeg.

These cheesy potatoes are the perfect holiday side dish. They’re great for Thanksgiving dinner, Christmas dinner or whichever fall or winter holiday you’re celebrating.

This is actually an easy recipe to make. The most difficult part is using the mandolin slicer, and there’s really nothing to it.

Just read the manufacturer’s instructions and make sure you’re using a guard so you don’t cut yourself. The rest of the recipe is super simple.

This potato dish is very similar to my Homemade Au Gratin Potatoes but with sweet potatoes instead. Both recipes are SUPER delicious and a treat at any dinner table.

Next time you’re looking for a dish to impress at your next holiday dinner then Homemade Sweet Potato Au Gratin is the way to go!

Sweet potato recipes are always a huge hit for the holidays! I enjoy making Old Fashioned Candied Sweet Potatoes, Homemade Sweet Potato Ice Cream and Southern Sweet Potato Pie!

What is Sweet Potato Au Gratin?

Sweet Potato Au Gratin is a dish cooked in the au gratin style. It contains layers of thinly sliced potatoes, about 1/8 inch thick.

The potatoes are layered into a baking dish with cream, cheese, garlic and thyme. Topped with more grated cheese then baked until golden brown and bubbly.

Gruyere, cheddar and parmesan cheese are popular choices when making au gratin dishes but I like to use Romano cheese for this recipe and my Homemade Au Gratin Potatoes.

The Romano cheese paired with cream makes for nice creamy au gratin potatoes.

Ingredients needed

• Sweet Potatoes – Try to find uniformly shaped sweet potatoes to make peeling and slicing easier.
• Heavy Cream – Heavy whipping cream makes a luscious cream sauce.
• Garlic – I definitely prefer fresh garlic cloves over garlic powder or granulated garlic here.
• Fresh Thyme – I love the flavor of fresh thyme with au gratin potatoes. I prefer fresh but if you only have dried then use about half the amount called for.
• Fresh Sage – A small amount of fresh sage goes a along way. It adds just a hint of flavor.
• Kosher Salt – Salt is a potatoes best friend. It helps bring out all of the flavors in this cream potato dish.
• Black Pepper – Just a pinch of black pepper for flavor. I like to use coarse ground black pepper.
• Nutmeg – Nutmeg and cream sauce are a classic combo. It’s just enough to provide a little background flavor but not to taste like you’re eating nutmeg.
• Romano Cheese – I love using Romano cheese in this recipe and Homemade Au Gratin Potatoes! It’s a method I learned from a friend years ago working in his butcher shop and it’s stuck ever since. It really makes the best au gratin potatoes in my opinion. I normally find it in the specialty cheese section of the grocery store.

Equipment needed

• Casserole Dish – I use a 10×7 ceramic baking dish but anything near that size will work.
• Mandolin – You will need a mandolin slicer to slice your potatoes to the proper thickness. They are easy to use but it’s also important you ALWAYS use the guard to prevent cuts.
• Peeler – The sweet potatoes need peeled and a peeler is the easiest fastest way to get that done.
• Sharp Knife – The herbs and garlic need chopped. I use a chef knife for all three things.
• Cutting Board – Using a cutting board that is high quality and comfortable for you is super important. My favorite two boards are a Boos Block and a large white board with grips.
• Small Sauce Pan – You can use a small sauce pan or pitcher to mix the cream sauce.
• Ladle – I use a ladle to add the cream to each layer.
• Whisk – Use a whisk to mix the cream sauce ingredients.

Tips

• Make sure to press the sweet potatoes down under the cream mixture a couple times during the layering and at the end. You want the cream to slightly cover the top of the potatoes.
• The cream sauce will taste salty. That’s okay, the potatoes will soak that all up and it will not be salty after it’s cooked.
• For the best results, give the cream mixture a stir right before each addition. The garlic sinks to the bottom and this makes for more evenly distributed flavor.
• You can make this recipe up to 3 days ahead of time.
• Reheat them in the oven or microwave. Place the potatoes in an oven safe dish, cover in foil and heat in a 400°F oven for about 10 – 15minutes.

How to make Sweet Potato Au Gratin

Preheat the oven to 400°F then spray an 10×7 baking dish with non-stick cooking spray. Whisk the heavy cream, garlic, thyme, sage, salt, pepper and nutmeg together in a pitcher or small sauce pan.

The cream mixture should taste fairly salty. Once it’s baked with the sweet potatoes it turns into a delicious white sauce and will not be salty.

Slice the sweet potatoes to about 1/8th of an inch thick on a mandolin using a guard. Stir up the cream mixture and ladle a small amount into the bottom of the dish, tilting the pan around so the liquid covers the bottom.

Layer the sweet potato slices into the pan in a shingle style layer. Ladle a small amount of cream over the layer of potatoes then sprinkle a little Romano cheese on top.

I like to stir up the cream mixture before each addition because the garlic tends to sink to the bottom.

Add another layer of sweet potatoes in the opposite direction. Ladle a small amount of cream then sprinkle with a little bit of Romano. Even layers make the dish more beautiful.

Repeat this process, alternating the direction of the sweet potatoes in each layer, until all potatoes and cream are used.

Sprinkle the remaining Romano cheese over the top then bake for 40 minutes uncovered. This will give you a nice golden brown top.

Cover the dish with aluminum foil then bake an additional 15 minutes. At this point you should have tender potatoes and can remove the dish from the oven.

Cooking time can vary slightly from oven to oven. Insert a butter knife or toothpick; you want it to go in and come back out without any resistance.

Let them cool for 30 minutes to set the layers then you can cut into the cheesy potato goodness. They can be enjoyed warm or at room temperature.

Need a sweet & savory sweet potato recipe? Sweet Potato Pudding is just that with sage brown butter and toasted marshmallows.

Can you make ahead of time?

Yes, you certainly can! You can make this au gratin recipe up to 3 days ahead of time.

Make them as directed, let them cool on the counter to room temperature then cover tightly with plastic wrap and store in the fridge for up to 3 days.

To reheat them, preheat the oven to 350°F, cover the dish with plastic wrap then aluminum foil and bake for 20-25 minutes or just until warm in the center.

Storage

You can be store these in the fridge for up to 5 days after making. Let the au gratin potatoes cool completely then wrap tightly with plastic wrap and store in the fridge.

They can be reheated in individual pieces in the microwave or you can reheat in the oven at 350°F, covered, just until warm.

When to serve Homemade Sweet Potato Au Gratin

These are a great side dish for a holiday dinner such as Thanksgiving or Christmas. I also enjoy eating these throughout the fall and winter months.

They go really well at the holidays alongside Glazed Shallots, Traditional Bread Stuffing and Cranberry Orange Sauce!

FAQ

What is the difference between au gratin potatoes and scalloped potatoes?

The two dishes are fairly similar. They both use thinly sliced potatoes, cream and are baked in a casserole style dish.

The main difference between the two is the use of cheese. Au gratin potatoes have grated cheese between the layers of potatoes and scalloped potatoes do not.

Other types of cheese are often used in au gratin potatoes as well such as gruyere or sharp cheddar cheese.

Au gratin potatoes also have grated cheese sprinkled over the top of the dish and some recipes call for bread crumbs as well.

As Southern Living Magazine says, “However you make them, both dishes are comforting, go-with-anything sides, especially around the holidays…”

My version of this recipe uses grated Romano cheese with no breadcrumbs. This is a gluten free recipe.

How do I slice potatoes for au gratin potatoes?

Au gratin potatoes need to be sliced very thin. About 1/8 inch is best.

The easiest way to achieve this is using a mandolin slicer. You can also use a clean meat slicer if you have one.

Either way, be sure to use the guard while slicing to avoid an accidents.

Slicing the potatoes this thin creates beautiful layers and ensures proper cooking in the amount of time allotted.

What kind of cheese should I use?

There are several options for this. You definitely want to include a grated cheese.

For me, I love using grated Romano cheese for my traditional and sweet potato au gratin.

A few other popular cheeses include:

• Grated Parmesan
• Gruyere
• Sharp Cheddar

What to serve with Homemade Sweet Potato Au Gratin?

• Standing Rib Roast
• Cranberry Orange Sauce
• Glazed Shallots
• Traditional Bread Stuffing