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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 (6 reviews)

  • 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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