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With layers of thinly sliced sweet potatoes baked in a creamy cheesy sauce this Sweet Potatoes Au Gratin twist on the classic French dish is thoroughly indulgent and practically impossible to dislike.
Baked to perfection, this rich & delicious sweet potato casserole dish is sure to be a hit at your next meal. And it takes just a few kitchen tools with a bit of prep work to easily make it.
I was given a copy of French from the Market by Hillary Davis, but all my opinions are my own.
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Please let me know if you have any questions about this recipe. I read all the comments myself and I try to help as soon as I can. I have readers from all levels of comfort and experience in the kitchen on my site, and I’ve tried to answer some of your questions already in the post. But if I’ve missed anything, please feel free to leave a comment and ask.
Au Gratin, Dauphinoise, or Scalloped potatoes?
So, my first question when I decided to make this recipe was, what’s the difference between an Au Gratin, dauphinoise, and scalloped potato recipe?
It can get so confusing with all the different names out there. Plus, so much of the information is conflicting. And to add to the confusion, there’s potatoes dauphine (deep-fried potato puffs), gratin de pommes de terre, funeral potatoes, and potato pavé (a taller dish where the potatoes have been cooked so they almost melt into each other).
Au Gratin
Potatoes au gratin, or au gratin potatoes are made with pre-cooked thinly sliced potatoes in a cream sauce using cheese. Fresh breadcrumbs can be sprinkled on top of the dish before it goes into the oven.
The only real difference between dauphinoise and au gratin is that one is pre-cooked, and the other isn’t.
Au gratin potatoes are often referred to as funeral potatoes as well.
Also, the term “au gratin” refers to any dish with cheese and breadcrumbs that’s browned on top.
Dauphinoise
Dauphinoise (daa·fuhn·waa) potatoes is basically the French version of saying potato casserole with cream and cheese.
It’s made with raw uncooked, thinly sliced potatoes arranged in a shallow baking dish, that are cooked in a cream sauce (not a bechamel) with a greater proportion of sauce to the potatoes.
Scalloped potatoes
Scalloped potatoes typically contain cream, often from a bechamel sauce, but can also use stock instead of dairy. Scalloped potatoes do not typically contain cheese. Check out my Scalloped Potatoes recipe.
Potatoes by any name
When it comes to potatoes, I say bring it on! Most people I know like just about any form of potato.
In the book she calls this recipe a Sweet Potato Dauphinoise, on page 180. After doing my research into the names I decided to rename it. But, as always, feel free to call it whatever you like. It’s delicious either way!
You’ll also love my Potato Stacks, Mashed potato casserole, and Potato and Onion Layer Bake.
French from the Market
{affiliate} French from the Market by Hillary Davis brings you the best of traditional French cooking. Provincial cuisine based on produce and foods fresh from the market, simply prepared, and delicious for everyday dining at home with beautiful colorful pictures of fresh produce.
Everything in this book makes me want to run out to my local farmer’s market and gather up all the fresh produce to make these recipes.
There are 100 plus recipes for starters, soups, salads, fish, poultry, meats, vegetables, and desserts in this cookbook, along with detailed instructions and tips.
All of these recipes will allow you to embrace French cuisine. I can’t wait to try Asparagus with Blood Orange Maltaise Sauce on page 169. The Smoked Salmon and Avocado Mousse in a glass on page 38 looks amazing and I’ll be making that really soon!
A lot of these recipes remind me of when I worked in the French café. Easy to make, great fresh fruits and veggies. And they are impressive yet so familiar.
I think this is a book that every cook will enjoy! So many fresh flavors and textures. And such colorful vivid images!
More French recipes
If you want to try more French recipes, be sure to check these out!
How to make
This creamy cheesy sweet potato casserole is simple to make and so impressive.
The full printable recipe ingredients and instructions are available in the recipe card at the bottom of the post. You can find important tips and tricks in the post.
sweet potatoes
Pro tip: when you buy the sweet potatoes, look for ones that are consistent in shape, meaning they don’t have fatter and thinner parts. And, if you can find the fatter ones rather than the skinny ones, you’ll get larger, rounder slices instead of thin, oddly shaped ones.
Slice the potatoes. I like the mandoline for this. It makes nice even slices. But be careful when using it, and always be sure to use the guard on the mandoline.
To measure, place them in a large glass measuring cup and try to fill it completely. 4 cups is about 2 large sweet potatoes. And, a little more or less potatoes will work just fine.
Preheat the oven to 350º F. Coat an 8 x 10-inch baking dish generously with butter. These can also be baked in a 13×9 casserole.
Bring a large pot full of water to a boil over high heat, gently drop in the sweet potato slices, and boil for 6 minutes.
Par boil the potatoes until fork tender. Cooking the sliced potatoes before baking them ensures they are tender by the time the casserole is done cooking.
Mornay sauce
I like to measure out all the herbs and spices before I start making the sauce.
In a saucepan over medium heat, melt the butter. Whisk in the flour until coated and cook for 2 minutes, whisking constantly. Pour in the milk and, while whisking, cook for about 4 minutes, or until the sauce thickens.
Stir in the garlic, honey, mustard, nutmeg, thyme, and fine sea salt to combine.
Add the Gruyère and stir until it melts. You have just made a Mornay sauce; the same one you would make for mac and cheese.
Pro tip: It’s always best to grate your own cheese. It will melt better, as store-bought pre-shredded has an anti-caking agent which prevents the cheese melting as well as it naturally would.
Layer the casserole
Layer one-third of the sweet potatoes in the bottom of the prepared baking dish and pour one-third of the sauce over the sweet potatoes. Arrange another third of the sweet potatoes in a layer over the sauce and pour another one-third of the sauce on top.
Create a final layer of sweet potatoes, covering them with the remaining sauce. Sprinkle the Parmesan over the top.
Bake it up
Cover the baking dish with a lid or aluminum foil and bake for 45 minutes to 1 hour 30 minutes, until the sweet potatoes are tender, depending on the thickness of the sweet potatoes. During the last 15 minutes or so, remove the cover while baking so the casserole browns a bit.
Check to see if it’s done by inserting a knife into the center and it should come out clean, with no resistance.
The baking time will differ depending on thickness of the slices, the shape of dish, the heat retention of baking dish, temperature of the oven, etc. That’s why there’s such a range in cooking times.
Let rest for 15 minutes before serving. Be patient here; I know it smells so good and you want to dig in, but wait! If you dig in while the dish is piping hot, you run the risk of it being soupy. Giving the dish time to cool allows the potatoes to soak up some of the sauce and the dish will firm up.
Can I make this ahead?
Yes! This is a great make ahead dish for holidays, family gatherings, and special dinners.
Bake up the dish as directed. Allow to cool completely, cover it tightly with cling wrap. And pop in the fridge.
Remove it from the fridge about 1 hour before you want to heat it. Reheat covered in foil in a 350º F oven for 20 to 30 mins or until hot, then remove foil and bake until cheese is golden.
Leftovers
Any leftovers will keep in an airtight container in the fridge for up to 5 days.
Reheat leftovers in the microwave or in the oven.
Can I freeze it?
I don’t recommend freezing this dish. Cream sauces tend to separate and become grainy with thawing and reheating.
Changes to the recipe
There are a lot of ways that you can customize this dish as well.
Double the sweet potato for a hearty veggie filled dish.
Try slicing the sweet potatoes thicker or thinner for different textures.
Add in blue cheese, tomatoes, parsnips, kale, spinach, zucchini, or apple slices into the layers. A sprinkling of Herbs de Provence would add a lovely touch.
Top the dish with toasted pecans for a nice pecan topping.
Reduce the fat in the dish by swapping the whole milk for low-fat milk or by using reduced fat cheeses. But be aware, this will make the dish not as rich and thick.
Can I use regular potatoes instead of sweet potatoes?
Yes, traditionally this is made with thinly sliced starchy potatoes like russet potatoes.
You might need to adjust the cooking time slightly, as regular potatoes tend to cook a bit faster than sweet potatoes.
Can I make this dish vegan or plant-based?
Yes, there are a lot of parts you’ll need to swap out. Use plant-based butter, unsweetened plant-based milk, and vegan cheeses.
Serving suggestions
This side dish pairs perfectly with rich meaty dishes like Smokehouse style beef or rolled stuffed turkey. Serve it with a nice Arugula Salad or Asparagus Pecan Salad on the side.
It’s also perfect for holiday dinners! And in case you’re seeing making Thanksgiving dinner, be sure to take look at these Classic Thanksgiving Side Dishes. And don’t forget the Libby’s Pumpkin Pie Recipe.
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Recipe
Sweet Potatoes Au Gratin
Ingredients
- 4 tablespoons unsalted butter plus more for the baking dish
- 4 cups thinly sliced peeled sweet potatoes sliced about ¼ to ½ inch thick, about 2 large potatoes
- ¼ cup all-purpose flour
- 2 ½ cups whole milk or half-and-half
- 3 garlic cloves pressed or minced
- 2 tablespoons honey
- 2 teaspoons Dijon mustard
- 1 teaspoon freshly grated nutmeg
- 2 teaspoons fresh thyme leaves
- 1 teaspoon fine sea salt
- 1½ cups grated Gruyère Raclette, or Emmental cheese
- ½ cup grated Parmesan cheese
Instructions
- Preheat the oven to 350 º F. Coat an 8 x 10-inch baking dish generously with butter.4 tablespoons unsalted butter
- Bring a large pot full of water to a boil over high heat, gently drop in the sweet potato slices, and boil for 6 minutes.4 cups thinly sliced peeled sweet potatoes
- In a saucepan over medium heat, melt the butter. Whisk in the flour until coated and cook for 2 minutes, whisking constantly. Pour in the milk and, while whisking, cook for about 4 minutes, or until the sauce thickens. Stir in the garlic, honey, mustard, nutmeg, thyme, and fine sea salt to combine.4 tablespoons unsalted butter, ¼ cup all-purpose flour, 2 ½ cups whole milk or half-and-half, 3 garlic cloves, 2 tablespoons honey, 2 teaspoons Dijon mustard, 1 teaspoon freshly grated nutmeg, 2 teaspoons fresh thyme leaves, 1 teaspoon fine sea salt
- Add the Gruyère and stir until it melts. You have just made a Mornay sauce, the same one you would make for mac and cheese.1½ cups grated Gruyère
- Layer one-third of the sweet potatoes in the bottom of the prepared baking dish and pour one-third of the sauce over the sweet potatoes. Arrange another third of the sweet potatoes in a layer over the sauce and pour another one-third of the sauce on top. Create a final layer of sweet potatoes, covering them with the remaining sauce. Sprinkle the Parmesan over the top.½ cup grated Parmesan cheese
- Cover the baking dish with a lid or aluminum foil and bake for 45 minutes to 1 hour 30 minutes, until the sweet potatoes are tender, depending on the thickness of the sweet potatoes. During the last 15 minutes or so, remove the cover while baking so the casserole browns a bit. Let rest for 15 minutes before serving.
Notes
Nutrition
Nutritional information is based on third-party calculations, and should be considered estimates. Actual nutritional content will vary based on brands used, measuring methods, portion sizes, and more.
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