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Sweet Potato-Russet Potato Gratin with Horseradish & a Dijon Crust

Scott Phillips

Servings: eight as a side dish.



For the topping:

  • 1-1/2 cups coarse fresh breadcrumbs (from an airy, crusty loaf like ciabatta)
  • 2 Tbs. unsalted butter, melted
  • Kosher salt
  • 1 Tbs. Dijon mustard
  • 2 Tbs. grated Parmigiano Reggiano
  • 2 Tbs. chopped fresh flat-leaf parsley

For the gratin:

  • 2 Tbs. unsalted butter, plus 1/2 tsp. for the dish
  • 1 cup thinly sliced shallots (from 6 to 7 large)
  • Kosher salt
  • 2/3 cup heavy cream
  • 2/3 cup homemade or low-salt canned chicken broth
  • 2 Tbs. prepared horseradish
  • Freshly ground black pepper
  • 1 russet potato (12 oz.)
  • 1 sweet potato (12 oz.)
  • 1/3 cup grated Parmigiano Reggiano

Nutritional Information

  • Nutritional Sample Size based on eight servings
  • Calories (kcal) : 280
  • Fat Calories (kcal): 140
  • Fat (g): 15
  • Saturated Fat (g): 9
  • Polyunsaturated Fat (g): 1
  • Monounsaturated Fat (g): 5
  • Cholesterol (mg): 45
  • Sodium (mg): 790
  • Carbohydrates (g): 32
  • Fiber (g): 3
  • Protein (g): 6


Make the topping:

  • Combine the breadcrumbs, melted butter, and a pinch of salt in a bowl. Mix in the mustard and then the Parmigiano and parsley.

Prepare the gratin:

  • Heat the oven to 350°F. Rub a shallow 2-quart gratin dish with 1/2 tsp. of the butter. Melt the 2 Tbs. butter in a small saucepan over medium heat. Add the shallots and a big pinch of salt; cook, stirring frequently, until softened, limp, and somewhat golden. Whisk together the cream, broth, and horseradish; add to the shallots. Season with salt and pepper, stir to combine, and take off the heat.

Assemble and bake the gratin:

  • Peel the potato and sweet potato, cut each in half lengthwise, and slice each across into thin half moons. In a large bowl, combine the potato and sweet potato slices, 2 teaspoons salt, the Parmigiano, and the shallot cream. With a rubber spatula, mix gently but thoroughly and scrape into the prepared gratin dish, smoothing and pressing until evenly distributed.Cover with the breadcrumb topping.
  • Bake until the crust is deep golden brown, the juices around the edges are have subsided, and the potatoes are tender when pierced with a fork, about 1 hour. Let rest for 15 to 20 minutes before serving.


Rate or Review

Reviews (7 reviews)

  • butterscotch | 11/29/2019

    This is delicious. We upped the horseradish and mustard, as suggested in other comments, and still found the finished dish very mild. The one drawback of this lovely recipe is that it is quite labor intensive and not at all quick. It took two of us about an hour of pretty intensive work to peel and slice the potatoes and sweet potatoes, make the horseradish cream and the breadcrumbs, and assemble the gratin. And we found the one-hour baking time called for in the recipe in the recipe was not nearly long enough. After one hour, the vegetables were soft, but there was still too much horseradish cream pooled in the bottom of the baking dish; we had to bake the gratin for an additional 20 minutes to get the pooled cream to evaporate. I will make this again because the whole family enjoyed eating it but only when I'm not pressed for time.

  • JKinME | 05/20/2018

    I have been making this dish for Thanksgiving for years. My family loves it, even the members who don't like sweet potatoes. I usually up the horseradish and dijon, as others have noted, and I always make a double batch. Not sure how two potatoes can serve 8?

  • Kohola | 01/02/2017

    Very delish! I did what others suggested and used more dijon and 3 big tbsp of horseradish and it was perfect. I did use a teeny bit more potatoes (both) to make a bigger batch. Actually had this as a main dish with a side salad.

  • grlup | 01/14/2014

    I really wanted to like this but the first time I made it I was underwhelmed. Second time around I doubled the horseradish and added a bit more mustard and Voila! Perfect. It's not really too prep intensive and I make it the star of a meatless meal by adding a salad.

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