Savory Sweet Potato Gratin with Graviera

Savory Sweet Potato Gratin with Graviera

A savory sweet potato gratin layered with Graviera (or Gruyère), prosciutto, and a cream custard infused with sage, thyme, and nutmeg. Golden, bubbling, and make-ahead friendly.

Course Dinner, Holidays

Cuisine International

Prep Time 30

Cook Time 1 10

Rest 10

Total Time 1 50

Servings

Calories 535kcal

Author by Jenny Skrapaliori Graves

Equipment

10.5" x 7.5" baking pan or gratin dish

Ingredients

2½ lb 1.1 kg sweet potatoes (about 6 medium), peeled or scrubbed, sliced ⅛ inch (3 mm) thick
3 tablespoons butter softened
1½ cups about 6 oz / 170 g grated Graviera cheese, or Gruyère
4 oz 115 g prosciutto cubetti (diced prosciutto)
2 cups 480 ml heavy cream
6-8 fresh sage leaves plus a few small leaves for garnish (optional) — or 1 teaspoon dried sage
4-5 fresh thyme sprigs — or 1 teaspoon dried thyme
3-4 whole cloves
4 garlic cloves minced
1 teaspoon ground nutmeg
3 large eggs
Salt and freshly ground black pepper

Instructions

Heat the oven to 400°F (200°C).
Infuse the cream: In a medium pot, combine the cream, sage leaves, thyme sprigs, cloves, garlic, nutmeg, and a pinch of salt. Bring to a gentle simmer and cook until slightly reduced and fragrant, about 10 minutes. Strain through a fine sieve; discard the herbs and cloves.
Make the custard: In a large bowl, lightly whisk the eggs. Slowly pour in the warm cream, whisking constantly so the eggs don't scramble. Set aside.
Prep the dish: Generously butter the baking dish. Sprinkle about ¼ cup of the Graviera over the bottom.
First layer: Arrange a third of the sweet potatoes in the dish, slightly overlapping. Season with a pinch of salt and pepper. Pour over ⅓ of the custard, then sprinkle with ⅓ cup Graviera and ¼ cup prosciutto.
Second layer: Repeat with another third of the sweet potatoes, salt and pepper, ⅓ of the custard, ⅓ cup Graviera, and ¼ cup prosciutto.
Third layer: Top with the remaining sweet potatoes, salt and pepper, the remaining custard, ⅓ cup Graviera, and the remaining prosciutto.
Bake covered: Cover with a buttered sheet of foil and bake until the sweet potatoes are tender when pierced with a knife, about 40 minutes.
Bake uncovered: Remove the foil and sprinkle with the remaining Graviera (about ¼ cup). Bake until golden brown and bubbling and the center reaches 160°F (71°C), 25–30 minutes.
Rest: Let the gratin rest 10–15 minutes so the custard sets. Scatter with small sage leaves, if using, and serve.

Notes

Make ahead: Assemble up to a few hours ahead, cover, and refrigerate; add about 10 minutes to the covered bake if it goes in cold. Or bake fully a day ahead, refrigerate, and reheat covered at 350°F (175°C) for 20–25 minutes.

Cheese swaps: Gruyère, Comté, Emmental, or sharp white cheddar.

Vegetarian: Skip the prosciutto, or swap in sautéed mushrooms or caramelized onions.

Doneness: Because the custard contains eggs, the center should reach 160°F (71°C).

Nutrition is an estimate and varies with the products used.

Nutrition