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Horseradish-Dijon Mashed Potatoes with Caramelized Onions

These showstopping mashed potatoes make the perfect side dish to just about any hardy entrée! I’m officially calling these my Horseradish-Dijon Mashed Potatoes with Caramelized Onions. I know the title is a mouthful, but even with all those words it still can’t contain the awesomeness of this dish’s flavor profile! The bold, tangy notes in Horeradish-Dijon combo and the sweet, earthy flavor of the onion balance well in the creamy mashed potato base. Try it with everything! I’m thinking it would pair amazingly with fish, stuffed pork chops over venison loin, and even pot roast.


Horseradish-dijon mashed potatoes with caramelized onions, recipe by Stacy Lyn Harris

How to Make the Perfect Mashed Potatoes

I have a few tricks for making just-right, smashingly great mashed potatoes. Of course, you have to start with the best potato out there. My choice for mashed potatoes is the good-old russet, though the buttery Yukon potato can make a great choice as well.

Don’t boil the potatoes for too long. They get somewhat waterlogged, then turn mushy and grainy. Just keep your eyes on them as they boil. It usually takes my potatoes about 20 minutes before they are ready to drain.

I like to leave mine in the drainer for at least 5 minutes, because dryness is really the key to getting a good texture to your mashed potatoes. Once dry, the potatoes can soak up the warm cream, butter, and all the other amazing flavors in this recipe (horseradish, dijon, onions, etc.).

Make sure all the ingredients you’re adding to the potatoes are warm. This will keep the potatoes warm for dinner and prevent the undesirable gummy texture from developing.

Another way to reduce the chance of gluey potatoes is to avoid adding too many liquid elements to the potatoes and refrain from over-mixing and over-whipping. I know that sounds counter-intuitive, but believe me, I know! I’ve ruined this recipe too many times to count. I’ve failed every possible way in the kitchen. Not kidding!

If you’ve never had horseradish in your potatoes, you simply don’t know what you’re in for. It’s a subtle effect but it adds such an interesting depth and earthiness to the dish. With the caramelized onions and the dijon, this is the perfect bed for just about any protein. Since the caramelized onions add a good bit of sweetness, the horseradish and dijon play the role of balancing out the flavors. I cannot wait for you to try this. You’ll never look at mashed potatoes the same way again!

Horseradish-Dijon Mashed Potatoes with Caramelized Onion

Prep Time

15 mins

Cook Time

40 mins


Side Dish


American, Southern


caramelized onions, dijon, horseradish, mashed potatoes


8 people


-114 kcal


  • 3/4 cup room temperature butter 1 1/2 sticks, divided
  • 4 large yellow onions divided
  • 5 sprigs fresh thyme
  • Kosher salt and pepper to taste
  • 6 russet potatoes peeled and cut into 2-inch cubes
  • 1 cup heavy cream
  • 3 tablespoons Dijon mustard
  • 1/4 cup horseradish
  • fresh parsley for garnish, chopped


  1. Peel and dice three of the onions. Peel and cut the remaining onion in rounds. You will be cooking these onions in separate skillets. The diced onions will be stirred into the mashed potatoes and the onion rounds will top the potatoes. In a large skillet, add 2-3 Tbsp butter over medium heat. Add diced onions to pan, and sautè 3 minutes. Lower the heat to medium-low and sautè for about 20 minutes or until the onions are caramelized (dark golden-brown and soft). Season with the leaves of 3 thyme sprigs. 

  2. In a large skillet, add 2-3 Tbsp butter over medium heat. Add diced onions to pan, and sautè 3 minutes. Lower the heat to medium-low and sautè for about 20 minutes or until the onions are caramelized (dark golden-brown and soft). Season with the leaves of 3 thyme sprigs. 

  3. While the onions are cooking, add potatoes to a pot, and cover potatoes with water. Cover the pot with a lid and bring potatoes to a boil. Once the potatoes begin to boil, uncover and continue to boil for about 20 minutes, or until potatoes can be easily pierced with a knife. Drain the potatoes and allow to dry for about 5 minutes, then return to the pot.

  4. In a measuring cup or bowl, add cream and heat in the microwave for about 1 minute. Always add warm cream to hot potatoes so they don’t cool before you eat them and to keep from potatoes from becoming gummy. 

  5. Add 6 tablespoons (3/4 stick) butter to the hot potatoes and begin to mash with a potato masher. When the butter is melted, add 3/4 of the hot cream, horseradish, dijon mustard, and diced caramelized onions, then mash the ingredients and potatoes with a potato masher until incorporated. Don’t over-mix or over- whip if using a mixer or you will get gummy potatoes.  Add more of the cream until you reach the consistency you like. Taste for seasoning. Add salt and pepper to taste. Garnish with chopped parsley.

4 responses to “Horseradish-Dijon Mashed Potatoes with Caramelized Onions”

  1. Lori says:

    Do you use fresh horseradish or prepared?
    Haven’t made it yet….

  2. […] this over Horseradish-Dijon Mashed Potatoes with Caramelized Onions alongside Roasted Asparagus or Brussels Sprouts with Beer-Glazed Bacon Topping and a show-stopping […]

  3. […] For a beach trip to go as planned, two things have to happen. First, our family needs to have fun, relax, and enjoy our time with each other. Second, we must return home with loads of yummy fish to eat. I’m happy to report that our last beach trip was a huge success! We came back with a huge supply of redfish to feast on, so I made this Blackened Redfish dish! Oh how I love a blackened fish—tasty with a perfectly crunchy crust, and it just feels healthy while you’re eating it! Light, healthy proteins like fish are so great! Adding to the Blackened Redfish experience is this amazing, creamy caper butter sauce. Try it with my Horseradish Dijon Mashed Potatoes. […]

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