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Sweet Potatoes Au Gratin

Renée Robinson

Luscious is the Word That Comes to Mind Here.

I’ve made many gratins using white potatoes, but decided to try one with sweet potatoes. I really only like sweet potatoes when they’re cooked with savory ingredients. I find that adding additional sweetness to them causes them to be too cloying for my personal taste, so I figured they’d work well in a classic gratin. 

I thought that Gruyère would be a good choice for the cheese in this because it has a nutty flavor and seemed like a natural flavor combination with sweet potatoes. I used less cheese than I normally do when making a potato gratin because I didn’t think sweet potatoes would need it due to the amount of flavor they have all on their own. 

Plenty of cream seemed like a necessity if I was going to get that creamy texture I love in a gratin. I always go heavy on the cream. I don’t like a solid block of potatoes. I prefer them to be swimming in rich creamy sauce.

Besides salt and pepper, a little fresh minced rosemary and thyme were all that was needed to enhance the flavor of both the sweet potatoes and the sauce.

I really felt this would need some crunch and chopped up some toasted pistachios for sprinkling on top when it came out of the oven. I don’t know if you’ve ever tasted freeze dried green peppercorns, but I’m crazy about their flavor and texture. They seemed like a perfect fit here. But if you don’t have them you can substitute regular dried green peppercorns, or even a little lesser amount of crushed black peppercorns would work.

And while I know this sounds crazy, I also chose to sprinkle a teaspoon of cocoa nibs * on top. Hear me out. The flavor of cocoa nibs is very deep with a slight bitterness. I couldn’t help but feel they’d be a perfect match for the sweetness of the potatoes and the nutty richness of the sauce. Plus, they provide a great textural bit of crunchiness. 

So, what did we think of the final result? Well, we all think this is about as delicious as it gets. One member of my family is not a fan of sweet potatoes, but loved these. As I said, I prefer nothing sweet added to sweet potatoes and it proved to be true here yet again. Their flavor is earthy and the cream and cheese accentuate that flavor rather than obscuring it. The toppings put this over the top. They added another textural and flavor dimension that made these sweet potatoes noteworthy. 

With a dish this rich, I kept everything else very simple. Halfway through the baking time of the sweet potatoes, I popped a sheet pan full of seasoned chicken thighs into the same oven and they were finished when the potatoes had cooled a little and were ready to be served. A very simple light salad rounded out the meal. I’m not kidding when I say I could have eaten these as my main course. While that probably wouldn’t have been the healthiest of options, it would have been very deeply satisfying.

*Disclosure: I only recommend products I use myself and all opinions expressed here are my own. This post may contain affiliate links that, at no additional cost to you, may pay me a small commission and help support the costs of this website. Read full privacy policy here.

Sweet Potatoes Au Gratin

Recipe by Renée Robinson



Sweet potatoes are layered with heavy cream and gruyere cheese and then topped with pistachios, freeze dried green peppercorns, and cocoa nibs. You've gotta try it. Insanely delicious.

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  • 3 tablespoons salted butter, divided

  • 2 pounds sweet potatoes, peeled and sliced into 1/8 inch thick rounds (I used a mandolin)

  • 2 cups heavy cream

  • 1 1/2 teaspoons fresh rosemary leaves, minced

  • 1 teaspoon fresh thyme leaves, chopped

  • 1 teaspoon fine sea salt, approximate measurement

  • Black pepper

  • 5 ounces Gruyère cheese, shredded

  • 2 tablespoons toasted and salted pistachios, roughly chopped

  • 1 teaspoon freeze dried green peppercorns, roughly crushed, or regular dried green peppercorns, crushed

  • 1 teaspoon cocoa nibs *


  • Preheat the oven to 425° with a rack in the center.
  • Butter a 2 quart casserole dish with 1 tablespoon of the butter.
  • Layer 1/3 of the sweet potatoes in overlapping rows in the bottom of the dish followed by 1/3 of the cream, a healthy sprinkle of salt and a few grinds of black pepper, 1/3 of the cheese, and 1/3 of the rosemary and thyme. Dot with 1/3 of the remaining butter, which has been cut up into pieces. Continue layering in this manner until all the ingredients are used.
  • Bake for 50 to 55 minutes (until the potatoes are tender and the top has browned). Remove from the oven and let sit for 10 minutes. Sprinkle on the pistachios, green peppercorns, and cocoa nibs. Serve. And Enjoy!


  • 2 Quart Casserole Dish

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