Sweet Potato Gratin with Brown Butter, Sage, and Pecan-Parmesan Crust
Crisp-edged sweet potato slices bake in a silky cream sauce infused with browned butter and fresh sage, topped with a toasty pecan-Parmesan-panko crust that adds crunch and a nutty finish. The contrast of tender, slightly caramelized potatoes and a golden, savory topping delivers cozy autumn flavors with a refined texture.
Swap-ins are easy: use half-and-half for a lighter sauce or replace pecans with walnuts if preferred. For extra depth, stir 1 tbsp of Dijon mustard into the cream or fold 30 g grated Gruyère into the topping before baking. This dish holds well—cover and refrigerate up to 2 days, then reheat covered at 175°C (350°F) until warm.
Serve this gratin alongside roasted turkey, glazed pork, or as part of a holiday vegetable spread; it also shines at potlucks and dinner parties. Make it a day ahead for less stress—top and bake just before serving for the freshest crunch and best presentation.
How to Make It
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1
Preheat the oven to 190°C (375°F). Butter a 23x33 cm (9x13 in) baking dish or similarly sized gratin dish.
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2
Peel the sweet potatoes and slice them 3–4 mm thick using a sharp knife or mandoline; place slices in a single layer on a sheet pan as you work to avoid sticking.
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3
Brown the butter: melt the butter in a medium skillet over medium heat, swirling occasionally until the milk solids turn deep golden-brown and smell nutty, about 4–6 minutes. Remove from heat and stir in sage leaves; let the sage crisp in the hot butter for 30–45 seconds, then transfer butter and sage to a small bowl (reserve the sage leaves for topping).
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4
Mince the garlic. In a bowl, whisk together the browned butter (straining out any large browned bits if desired), heavy cream, milk, minced garlic, nutmeg, salt, and black pepper until combined.
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5
Arrange half of the sweet potato slices in an overlapping single layer in the prepared dish. Pour half of the cream mixture evenly over the potatoes. Repeat with the remaining potato slices and pour the remaining cream mixture over the top, pressing the slices gently so they sit level.
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6
Cover the dish tightly with aluminum foil and bake for 30 minutes. Remove the foil and continue baking until potatoes are tender when pierced with a knife, another 10–12 minutes.
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7
While the gratin bakes uncovered, make the topping: pulse the pecans in a food processor or chop finely by hand. In a small skillet, heat the olive oil over medium heat, add panko and chopped pecans, and toast until golden, 3–4 minutes. Remove from heat and stir in the Parmesan cheese and reserved crisp sage leaves (reserve a few sage leaves for garnish if you like).
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8
Sprinkle the pecan-Parmesan mixture evenly over the baked gratin and return to the oven for 8–10 minutes, or until the topping is golden-brown and crunchy.
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9
Let the gratin rest 10 minutes before serving to allow the sauce to settle. Garnish with any reserved whole sage leaves and serve warm.