Sweet Potatoes Au Gratin

I know what you’re all thinking right now: “Uhhh what?! Sweet potatoes au gratin on a baking blog specifically about afternoon tea? What is she thinking?” I thought the same thing when I mentioned this recipe to my amazing friend Kat (remember her from The T Room?). When I told her that I had come up with this incredible new recipe for Thanksgiving and how I wished I could share it on my blog because everyone should make it for Thanksgiving dinner. And yeah I stretch the “afternoon tea” part of this blog when it comes to baking recipes, but trying to justify sweet potatoes au gratin? That was going too far. And what did Kat say?

sweet potatoes au gratin

sweet potatoes au gratin

“It’s your blog. You can post whatever the heck you want.”

The girl’s got a point. And Thanksgiving is all about giving isn’t it? So since I’m so thankful for all my supporters and my readers, I am going to give you this recipe that has nothing to do with afternoon tea. Though if this showed up on my savory tier at a tea house, I would think they were awesome and would forgive them for using mayonnaise and egg salad on the same plate as it.

This sweet potato dish won the recipe test my mom and I did to find a new sweet potato dish for the Big Meal. We’ve always made the sweet potato (or yams) casserole with the brown sugar topping, but this year I wanted to mix things up a little and try something savory with sweet potatoes instead of, well, sweet. We searched and we modified, we layered and we baked, we ate and we ate and we ate. And then we sent the contenders out into the world for more blind taste testing and voting. And, in the biggest shocker since The Red Wedding, the vote was unanimous! Everyone voted for this recipe, including my mom and me, and so this casserole dish of melt-in-your-mouth sweet potatoes with mellow sweet onions and mouthwatering combination of gruyere and parmesan cheeses will be featured on my Thanksgiving table. An automatic double batch because it’s that good. If you haven’t picked a sweet potato dish yet, here’s the gold star au gratin. And if you have, toss out your sweet and marshmellowed recipe and replace it with this instead.

No tricks, no tips, no warnings with this easy recipe. And it can easily be doubled or cut in half depending on the size of your feast!

sweet potatoes au gratin

sweet potatoes au gratin

sweet potatoes au gratin


  • 1 ½ cups heavy whipping cream
  • 1 minced garlic clove
  • 1 tsp chopped fresh rosemary
  • 1 tsp chopped fresh thyme
  • ½ tsp chopped fresh sage
  • salt
  • fresh ground pepper
  • 2 lbs peeled sweet potatoes or yams
  • ½ yellow onion, sliced thinly
  • 3 cups grated Gruyere cheese
  • ¼ cup grated parmesan cheese



Preheat oven to 375°F. Grease an 11 inch gratin dish.


OPTIONAL Caramelize the onions. In a small pan, heat a small amount of olive oil over a medium flame. Once beginning to smoke and shimmer, add the thinly sliced onions. Continue stirring onions occasionally so that the onions get nice and brown and reduced but do not burn. About 10 minutes in, toss in some salt. Onions should take about 30 minutes, so you can prep the other ingredients while you keep an eye on them.


In a medium saucepan over medium heat, combine cream, garlic, rosemary, thyme, sage, and a pinch of each salt and pepper. Heat until just boiling, stirring frequently, and then remove from heat.


Slice sweet potatoes 1/8 inch thick. Stir potatoes and cream mixture together.


Arrange 1/3 of potatoes in the base of the gratin dish, overlapping slightly. Sprinkle generously with salt and pepper. Top with half the onion, then 1 cup grated gruyere. Repeat layers using another 1/3 of the potatoes, salt, pepper, the rest of the onion, and another 1 cup grated gruyere. Top with remaining potatoes and salt and pepper. Press potatoes down slightly with a spatula. Pour half the remaining cream mixture over the potatoes.


Top with the final 1 cup grated gruyere and sprinkle ¼ cup grated parmesan over that. Cover dish with foil.


Bake for 45 minutes. Remove foil and bake for another 15-20 minutes until top cheese layers are browning. Let rest 10 minutes before serving.

2 comments on “Sweet Potatoes Au Gratin

  1. anon

    Looks delicious, and I don’t even like sweet potatoes. You made them in a way that I will want to do! Love having gruyer in there.

    1. Jenna

      made them for yesterday and have no leftovers! they are amazing :)

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