Prep 25m Cook 25m Additional - Ready In 50m
Servings 8 servings Calories 381.1

Caramelized onions give this incredible side dish a subtle sweetness, and the addition of horseradish gives it a little attitude! They make an absolutely fabulous side dish to prime rib, and have become a tradition every year at family holiday gatherings! To save time, the caramelized onions can be made ahead of time and refrigerated, then warmed before adding to the potatoes.

Recipe Ingredients

  • 3 tablespoons butter
  • 4 onion, sliced and separated into rings
  • 1 tablespoon white wine vinegar
  • ½ teaspoon ground dried thyme
  • 6 large baking potatoes, peeled and cubed
  • 1 tablespoon Dijon mustard
  • 2 tablespoons prepared horseradish, or to taste
  • salt and cracked black pepper to taste
  • ¼ cup softened butter
  • ¾ cup half-and-half

Cooking Directions

  1. 1 Melt 3 tablespoons butter in a large skillet over medium-high heat. Add the onions and cook for 5 minutes. Reduce heat to medium, and continue cooking, stirring frequently, until the onions have softened, and achieved a deep brown color, 15 to 25 minutes. Stir in vinegar and thyme, and cook for 5 minutes more.
  2. 2 While the onions are cooking, place cubed potatoes in large pot and cover with salted water. Bring to a boil, then reduce heat to medium-low, cover, and simmer until the potatoes can be pierced easily with a fork, about 20 minutes. Drain the potatoes in a colander, and allow to steam for a minute.
  3. 3 To finish the dish, transfer the potatoes to a serving bowl, and use a potato masher to mix with Dijon mustard, horseradish, salt and cracked black pepper until smooth. Mix in softened butter, caramelized onions, and half-and-half until onions are distributed evenly.

Nutrition Facts

  • Calories 381.1
  • Carbohydrate 60.8 g
  • Cholesterol 35.1 mg
  • Fat 13.1 g
  • Fiber 8.2 g
  • Protein 7.7 g
  • Saturated Fat 8.1 g
  • Sodium 160.9 mg
  • Sugar 7.3 g


  1. Wonderful wonderful wonderful potatoes. Made these for a dinner party to serve under Beef Burgundy. Simple easy tasty full flavored. I did use Yukon Gold potatoes instead of russets because that's what I had on hand this time around. Will most definitely make these again. It goes great with beef.
  2. We loved these potatoes! Beautiful rich color from the caramelized onions and deeply flavored. Definitely worth the extra effort and time it took to caramelize the onions. Just enough horseradish and Dijon to make these interestingly different, although I wouldn't hesitate to add more horseradish. I found I didn't need the extra butter at the - Read more ...
  3. Not very good at all!!! Will not make again
  4. very yummy. i scaled back to 6 servings and even opted to use 2 sweet vidalia onions over the 3 they suggested. it was plenty!!! also diced for ease of mixing and eating. omitted thyme since i didnt have it. served with flat iron steak w/ blue cheese chive butter (also from site) the first - Read more ...
  5. This recipe is fantastic! The only change I made was to substitute the white wine vinegar to half white cooking wine half cider vinegar because I didn't have white wine vinegar on hand. For the small amt. required I doubt it would have made much difference. But the flavor! I had 3 helpings my boyfriend - Read more ...
  6. Very nice twist on regular mashed potatoes. I omitted the horseradish (I forgot it) and all 5 of us loved it. Would suggest that the onions are cut up more than just 'sliced into rings' because it was somewhat difficult to eat with long rings. Very good flavor.
  7. Yummy side dish! I did have to add more 1/2 & 1/2 to make it creamy enough and also a bunch more horseradish because we like spicy!:)
  8. Fantastic recipe! I added a couple of cloves of fresh roasted garlic but add garlic to almost everything. I also added in a couple of dashes of white pepper!
  9. I thought this was really delicious. When I went to make it I found I had only 1 rather elderly potato. So I made instant mashed and added the seasonings. It was great and my guest had no idea I hadn't made it from scratch!
  10. This side dish was great - my family (kids, too!) liked it...a nice flavor with a little tang, but not too much for those who don't like spice. It didn't take too long to make and didn't have any unusual ingredients, that is nice when you have a family and house to keep up while - Read more ...

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