Sweet Potato Gratin

Sweet Potato Gratin

This sweet potato gratin is not your grandma’s potato gratin. (And by that we mean no disrespect to anyone’s grandma. We love grandmas. In particular little French grandmas who take to their local fromagerie for Gruyère when they make gratin and who toss it together without measuring or weighing but just by knowing.)–Renee Schettler Rossi

LC Thinly Sliced Spuds Note

We started to wonder, while editing this sweet potato gratin recipe, what our dear readers prefer to reach for when it come time to slice a lotta spuds. A food processor? A mandoline? A paring knife? Go on. Let us know in a comment below.

Sweet Potato Gratin

  • Quick Glance
  • Quick Glance
  • 45 M
  • 2 H
  • Serves 6 to 8
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Preheat the oven to 375°F (190°C). Butter the bottom and sides of a 9-by-13-inch (23-by-33-centimeter) or a 3-quart (3-liter) baking dish with butter.

In a small saucepan, combine the cream, broth, garlic, sage, and a good pinch of salt and pepper over medium-low heat and heat until small bubbles begin to appear around the edge of the pan and the liquid is steaming, 10 to 15 minutes. Remove from the heat and let steep while you prepare the potatoes.

Cut the rounded ends off each potato, then peel the potatoes. Using a food processor or mandoline fitted with the slicing blade, cut the potatoes crosswise into slices 1/4 inch (6 millimeters) thick. Layer the potato slices, alternating types, in the prepared baking dish. Pour the warm cream mixture through a fine-mesh sieve evenly over the potatoes and discard the garlic and sage. Cover the dish tightly with foil and bake for 45 minutes.

In a small bowl, toss together the Parmesan and Gruyère cheeses.

Uncover the potatoes and sprinkle with the cheeses. Continue to bake, uncovered, until the mixture is bubbly and thick, 25 to 30 minutes. Let stand for 10 minutes before serving.

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Recipe Testers' Reviews

A pretty, cheesy casserole. The final sweet potato gratin was tender and delicious, not to mention attractive. It made a wonderful dish for a fall weekend dinner. However, the time investment probably renders it less suitable to many households for a weeknight. It took longer than the time given in the recipe for the potatoes to be cooked through and the casserole to be sufficiently browned on top. A little extra time invested was worth it in the end. As I was slicing the potatoes, I realized there would be more sweet potato slices than russet ones, so I didn’t use the last sweet potato. I used 22 1/2 ounces sweet potatoes, which was more in line with the amount of russets. The combined potatoes filled the casserole dish nearly to the top. The shapes of the potatoes were also divergent. I couldn't find any fat garnet yams, so the slices were not as uniform as I would have liked. I salvaged the leftover sage and garlic from the simmered sauce to use in a pan sauce for pork chops that accompanied the gratin.

This sweet potato gratin is a straightforward recipe that yields a delicious and satisfying dish—a winner. I loved the subtlety of all the players in the gratin, which allowed the sweet potatoes to shine, as you would rightly expect from the name. The garlic and sage weren’t overpowering, and the combination of chicken broth and cream made a sauce that thickened perfectly at the end and wasn’t overly rich. The amounts for the cheeses were spot-on as well. If you don’t care for sage, I think fresh thyme or tarragon would be a lovely alternative. The attractive gratin with alternating colors of russet and sweet potatoes can be part of a holiday table or a casual supper on a weeknight.

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  1. For me the mandoline is the answer. I use it all the time when slicing lots especially when I want them sliced really thin and uniform. Used to use a knife, but the mandoline saves time.

  2. To slice anything that isn’t shaved, I find a really sharp knife does the trick. For something shaved (like fresh fennel), I have an old slicer my mother used and it’s crazy sharp, easily adjusted, very basic, but does the trick. I do use mandolines for some things, but I’m not fond of the food processor for slicing, because the food I’m trying to slice never seems to fit the chute. Don’t you just hate when that happens?

    1. I do hate that, gourmet goddess. I have two processors, a new-fangled one with a chute the size of a carrot and and old circa-1980s with a chute the size of a sweet potato. Guess which one I use most?

  3. I use a cheap mandoline for slicing potatoes, onions, apples & similar foods. I used it yesterday to make shards of parmesan for a salad. It does a great job as long as you watch out & don’t lose any fingertips!

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