Gluten-free, Side Dishes, Vegan/Vegetarian

Sweet Potato Onion Gratin

Loreto May 14, 2020

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Sweet Potato Onion Gratin. Outdoor cooking and backyard barbecues are underway. The aromas of grilling and the sounds of spring and summer are in the air. Today we are sharing a wonderful side dish that was inspired by a Food Network star. Come into our kitchen and let’s make this aromatic oh so flavorful dish!

Song of the day: “Born to be Wild” by Steppenwolf.

Sweet Potato Onion Gratin-in the plate and pan

Sweet Potato Onion Gratin! Take grilled sweet potato and onion and layer it in a baking dish separated by gooey cheese and cream spiced with grated horseradish and we have a side dish that will take you on the flavor town express! This dish has layer upon layer of taste bud tantalization surely making it a winner in my books!

Food Network inspiration…………

I am a big fan of the Food Network. I usually watch it daily and there are some favorites. One show, in particular, is Triple D with Guy Fieri. Gotta love that Camaro. I am a huge vintage muscle car fan. Anyway, Guy has quite a few different shows and one in particular really inspires me. It’s called Guys Big Bite. 

He cooks in his backyard kitchen furnished with all kinds of make me drool grilling and cooking appliances. One thing, in particular, is this wood fire oven. Oh, I could think of a plethora of things to cook in there, especially pizza! It sure would be a dream come true to be able to cook in his heavenly kitchen, hint hint, nudge, nudge, lol. Maybe take the Camaro out for a little drive, wink wink!

We can only dream…………….

Oh, I almost forgot where I was going with all this ranting. On one of his Big Bite shows, he did this sweet potato onion gratin. I was enthralled. I loved his use of the grill and mixing in some oven baking to bring some pretty amazing flavors and textures to a level that words can’t do it justice!

So come with us into our kitchen and let’s get cooking. Today, Sweet Potato Onion Gratin!

Sweet Potato Onion Gratin-in the pan-ingredients

This is what we will need…………….

  • Sweet potatoes
  • Onions
  • Canola oil
  • Butter
  • Gruyère
  • Asiago
  • Gouda
  • Horseradish
  • Whipping cream
  • Half & half cream
  • Dried thyme
  • Dried oregano
  • Salt & pepper

Now that we have all the ingredients guess what time it is. That’s right, cooking time!

Sweet Potato Onion Gratin-roasting

A little char goes a long way……………

  1. The first thing you need to do is season and oil the sweet potato and onion rounds. Preheat that grill and get these babies onto a grilling pan to get all flavored up. Look at that nice char. Do you know what that tells me?  Right again, you guys are good! Flavor and more flavor! These onion smell amazing I just want to eat them like that! However, I need them to finish this dish.

Layers upon layers of greatness………………

  1. Secondly, the assembly, which starts with some of the grated cheeses into the bottom of a greased baking dish. Then a layer of the grilled sweet potato, and grilled onion.
  2. Now more cheese and the process continues just like the last, sweet potato and onion!
  3. You will have three layers when you are done and a nice amount of grated cheese for the top, however, we need to prepare that cream.
  4. In a bowl combine whipping cream, half & half, grated horseradish, thyme, oregano,  and blend, then we have to pour it over the top! I just love how it’s making its way through all the spaces and I can only imagine the end result of flavor and texture. Crisp meets creamy, yum!
  5. Off to the preheated oven, at 350 degrees F covered in foil for the first stage of cooking. For the last stage, it will be uncovered to get all crusty beautiful!

We are so close to eating this Sweet Potato Onion Gratin!

Sweet Potato Onion Gratin-in the pan

Is that not just the most delicious thing you’ve ever seen?

Look at that top, the color, the texture. The aroma is amazing and my mouth is totally watering. I smell that horseradish and the buttery creaminess of the sauce. Those onions offering that familiar fair aroma. Let’s cut a piece and try it!

OMG, come on! This is killer. The sweet potato perfectly cooked. Soft, sweet, starchy. The onion waltzes so beautifully with its soft caramelized sweetness and that char on both of these vegetables adds a wonderful smokiness to the delectable mix.

Let’s talk sauce. That cream is the bomb. Its richness and accents of oregano, thyme, and especially that horseradish really offer some delicious hits. This is luxurious comfort side food heaven. I am so pleased with this. It turned out so well and it is my kind of side dish for backyard cooking and meals.

This Sweet Potato Onion Gratin would be great with BBQ ribs or chicken, or a wonderful grilled steak. Heck, I think it would work with anything grilled!

Final thoughts

It seems like an eternity since we have been in this quarantine. Thankfully, winter has gone and warm spring weather has arrived. At least we can enjoy our backyards and do some serious grilling! Thanks, Guy, for inspiring me, and for making this incredible dish! Keep doing what you do and love your tag lines! We really enjoy your shows! Hey, I am free next weekend, lol!

So, May long weekend is happening this weekend in Canada. Maybe you’re planning a nice picnic in your backyard. I think this dish would be the perfect addition to whatever you’re thinking of grilling! Want an utterly amazing side dish? Then think Sweet Potato Onion Gratin!

Happy May long weekend!

Enjoy and stay safe!


Song of the day: “Born to be Wild” by Steppenwolf.

Sweet Potato Onion Gratin-in the pan-whole

Sweet Potato Onion Gratin

  • Author: Loreto
  • Prep Time: 35 minutes
  • Cook Time: 1 hour 10 minutes
  • Total Time: 1 hour 45 minutes
  • Yield: serves 6-8 people 1x
  • Category: grilling/baking
  • Method: barbecue/oven
  • Cuisine: American
  • Diet: Vegetarian


Sweet Potato Onion Gratin.  Take grilled sweet potato and onion and layer it is a baking dish separated by gooey cheese and cream spiced with grated horseradish and we have a side dish that will take you on the flavor town express! This dish has layer upon layer of taste bud tantalization surely making it a winner in my books!


  • 2 large sweet potatoes peeled, washed, and dried and cut into 1/2 inch thick rounds
  • 2 medium Vidalia onions peeled and cut into 1/2 inch thick rounds
  • 1/4 cup canola oil
  • 2 Tbsp  unsalted room temperature butter
  • 1 1/2 cups half & half cream
  • 1/2 cup whipping cream
  • 4 Tbsp grated horseradish
  • 2 Tbsp dried thyme
  • 1 tsp dried oregano
  • 2 1/2 cups grated Gruyere, Gouda, Asiago cheese mixed
  • Salt, and pepper



  1. Pre-heat grill to medium to high heat. Pre-heat oven to 350 degrees F. Then grease a 9 x 13-inch baking dish with some butter.
  2. In a baking sheet sprinkle some oil over the onions and sweet potatoes and season with salt, pepper.
  3. Place sweet potatoes and onions on a vegetable cookie sheet on the grill and cook till veggies are slightly charred and cooked halfway. Roughly 2 minutes a side.


  1. In a large bowl combine half & half cream, whipping cream, horseradish, salt and pepper, 2 tsp salt and 1 tsp black pepper, thyme, and oregano. Blend well.


  1. Sprinkle some of the cheese mixture into the bottom of the greased baking dish. Layer 1/3 of the sweet potato and onion then sprinkle some cheese and repeat until you get three layers.
  2. Finish the top with more cheese blend. Then slowly pour the cream mixture over the top.


  1. Cover the dish with foil paper and bake in the oven for  35-40 minutes. Uncover and bake for an additional 15 to 20 minutes. Take out of the oven and let rest 15 minutes prior to serving.
  2. Ready to serve.



You can use any cheese you have on hand, preferably one that is a good melting cheese.

If you don’t like horseradish, substitute some grated ginger or garlic.

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Sweet Potato Onion Gratin-in the plate-closeup

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  • Avatar
    Reply Paige May 22, 2020 at 6:19 pm

    This looks SO delicious! I love how cheesy it looks too! YUM

    • Loreto
      Reply Loreto May 25, 2020 at 6:45 am

      Hi Paige. This dish is the epitome of cheesy delicious. Highly recommend trying this one. I know you won’t be disappointing!
      Have great cooking day!

  • Avatar
    Reply Anna May 24, 2020 at 2:34 am

    This dish was utterly delicious! We made it last night with some Gruyere cheese and it disappeared in minutes! Love that cheesey, yummy crust on top, and I’m already thinking of making this again!

    • Loreto
      Reply Loreto May 25, 2020 at 6:42 am

      Thanks Anna, I loved the way you described this experience and am so happy that you tried it. The same happened here, it was devoured!
      Thanks again for trying this recipe!
      Happy cooking!

  • Avatar
    Reply Kushigalu May 24, 2020 at 5:33 am

    One of my favorite combo. Love it. So delicious

    • Loreto
      Reply Loreto May 25, 2020 at 6:39 am

      Thanks, so glad you liked this one. It is a sure win dish where ever served!
      Have a great day!

  • Avatar
    Reply Jen May 24, 2020 at 11:11 am

    Between the char and the freshly grated horseradish this recipe is really special. Can’t wait to make it again.

    • Loreto
      Reply Loreto May 25, 2020 at 6:38 am

      Thank you so much. This recipe offers lots of flavor and texture surprises, and that herb cream mixture with the horseradish is pure heaven when cooked in between the layers!

  • Avatar
    Reply Charity May 24, 2020 at 7:42 pm

    I love Guy too! He really is the mayor of flavortown. I can see this dish was inspired by him because the ingredients sound so…flavorful. The horseradish really puts it over the top!

    • Loreto
      Reply Loreto May 25, 2020 at 6:32 am

      Thanks Charity for sharing. Yes that horseradish is amazing not to bold to take over, just enough kick to highten the flavor.
      Have a great cooking day!

  • Avatar
    Reply Sara May 24, 2020 at 10:39 pm

    What a gorgeous and delicious side dish! The cheese in the recipe are all some of my favorites, and we absolutely love onions in everything. It’s perfect for grilling out – thank you!

    • Loreto
      Reply Loreto May 25, 2020 at 6:30 am

      Thank you Sara, We too love onions and the fact that they are grilled is even better! That char adds such a level of flavor! A must try recipe indeed. I am still smacking my lips!

  • Avatar
    Reply Heidy McCalllum May 25, 2020 at 5:32 am

    This Sweet Potato Onion Gratin was really good and hot the spot because I have been so bored with some of our dinners. I love trying new flavor combos too!! I will be saving your recipe!

    • Loreto
      Reply Loreto May 25, 2020 at 6:14 am

      Thank you so much for trying this recipe. I am so glad that you are adding to your dinner repertoire!
      Happy cooking!

  • Avatar
    Reply Natalie May 25, 2020 at 7:28 am

    This looks fabulous. I absolutely love the flavors and you used all fresh ingredients and fresh horseradish… so delicious! I will definitely save this recipe.

    • Loreto
      Reply Loreto May 30, 2020 at 9:24 pm

      Thanks Natalie. I have never used fresh horse radish, but boy did I like it. It was nice a subtle and really hit the balance of flavors. As a whole love this dish, so delicious and total comfort food!
      Have a wonderful cook week!

  • Avatar
    Reply Jo May 25, 2020 at 8:34 am

    Love the clean and amazing flavors of this onion gratin! It sure looks very appetizing! Boy i’m hungry now!

    • Loreto
      Reply Loreto May 30, 2020 at 9:21 pm

      Lol, Thanks Jo, it makes me feel really good knowing that I made you hungry. It is not hard when you have a recipe like this. So excited for you to try it!
      Happy cooking!

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