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Sweet Potatoes au Gratin with Gruyère, Parmesan, and Pecans Recipe

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4.3 from 68 reviews

Sweet Potatoes au Gratin is a rich and creamy casserole that layers thinly sliced sweet potatoes with a fragrant thyme-infused cream sauce and melted Gruyere and Parmesan cheeses. This comforting dish combines the natural sweetness of the potatoes with the savory depth of nutmeg, garlic, and shallots, topped with crunchy pecans for an irresistible texture. Perfect as a decadent side for holiday meals or dinner gatherings.

  • Total Time: 1 hour 10 minutes
  • Yield: 6 servings

Ingredients

Sweet Potatoes

  • 4 sweet potatoes (around 1400g)

Cheese Sauce

  • 1 tbsp butter
  • 1 shallot, finely minced
  • 1 clove garlic, minced
  • 3 sprigs fresh thyme
  • 350 ml heavy cream
  • 150 g grated Gruyere cheese
  • 20 g grated Parmesan cheese
  • 1 tsp nutmeg, freshly grated
  • Salt, to taste
  • Black pepper, to taste

Topping

  • 20 g roughly chopped pecans

Instructions

  1. Prepare Sweet Potatoes: Peel the sweet potatoes and slice them thinly, about 3-4 mm thick, to ensure even cooking and layering in the gratin.
  2. Sauté Aromatics: In a saucepan, melt the butter over medium heat. Add minced shallot and garlic and sauté gently until translucent and fragrant, about 3-4 minutes. Avoid browning.
  3. Add Cream and Herbs: Pour in the heavy cream and add the sprigs of fresh thyme. Bring the mixture to a gentle simmer.
  4. Infuse and Season Sauce: Let the cream simmer for 5 minutes to infuse the thyme flavor. Remove the thyme sprigs, then stir in grated Gruyere, Parmesan, nutmeg, salt, and black pepper until the cheese fully melts and the sauce thickens slightly.
  5. Assemble the Gratin: In a buttered baking dish, arrange a layer of sweet potato slices, then pour a portion of the cheese cream over the layer. Repeat layering sweet potatoes and cream until all ingredients are used, finishing with a cheese-rich cream layer on top.
  6. Add Pecan Topping: Sprinkle the roughly chopped pecans evenly over the top layer for added crunch and flavor contrast.
  7. Bake: Preheat the oven to 180°C (350°F). Place the gratin in the oven and bake for 45-55 minutes, or until the sweet potatoes are tender when pierced with a fork and the top is golden brown and bubbling.
  8. Rest and Serve: Remove from the oven and let the gratin rest for about 10 minutes before serving. This helps the sauce to set slightly for easier slicing and better flavor melding.

Notes

  • Use a mandoline slicer if possible to get even thin slices of sweet potatoes.
  • The pecan topping can be substituted with breadcrumbs or omitted for a nut-free version.
  • For a slightly lighter dish, substitute half of the heavy cream with whole milk, but expect a less rich sauce.
  • Make sure to remove thyme sprigs before baking to avoid woody textures in the sauce.
  • Leftovers keep well in the refrigerator for up to 3 days and reheat nicely in the oven.
  • Author: Madelynn
  • Prep Time: 20 minutes
  • Cook Time: 50 minutes
  • Category: Side Dish
  • Method: Baking
  • Cuisine: French
  • Diet: Vegetarian

Find it online: https://allyumcooks.com/sweet-potatoes-au-gratin-with-gruyere-parmesan-and-pecans-recipe/