Sweet Potato & Gouda Gratin
A gratin only works when every layer cooks at the same pace, and with sweet potatoes that means slicing thin — really thin, a scant ⅛ inch — because the sweet potato is denser and starchier than a russet, and a thick slice will leave you with raw, hard centers while the top scorches. Thin, even slices shingle into a dish that steams and braises in its own cream, so there's no al dente surprise hiding in the middle. The second quiet trick is the cream itself: instead of dumping raw garlic into the dish where it can burn into bitter specks, you steep smashed garlic, thyme, rosemary, and a bay leaf in warm cream until the fat is perfumed, then strain. The herbs and aromatics give up their flavor and get pulled out, leaving a clean, fragrant custard behind. The Gouda is where people go wrong. Smoked Gouda is a low-moisture, semi-hard cheese — that's why it melts so lusciously — but it melts at a relatively cool 150°F and turns grainy and greasy if you push it past its comfort zone, when the proteins seize and squeeze out the fat. So we hold the oven at a steady 375°F, let the cream's moisture buffer the temperature, and pull the dish the moment the sweet potatoes are fork-tender and the center reads 185°F — the temperature where the starch has fully softened into silk. Bake it the day before if you like; it reheats into something even deeper. If you love this one, our Potatoes Dauphinoise is the classic cream-and-cheese cousin, Loaded Stuffed Sweet Potatoes doubles down on the sweet potato, and Brown Butter Garlic Confit Mashed Potatoes belongs on the same holiday plate.
Sides · Vegetarian, Gluten-Free, Make-Ahead, Thanksgiving • 1 hr 25 min
Nutrition (per serving)320Calories·21gFat·23gCarbs·9gProtein
Per serving. Values are approximate and calculated from USDA FoodData Central.
Ingredients
- For the herb-infused cream:
- 2 cups heavy cream
- ½ cup whole milk
- 4 garlic cloves, smashed and peeled
- 6 fresh thyme sprigs
- 1 fresh rosemary sprig
- 1 bay leaf
- ¼ teaspoon freshly grated nutmeg
- 1½ teaspoons kosher salt
- ½ teaspoon freshly ground black pepper
- For the gratin:
- 3 pounds sweet potatoes (about 4 large), peeled
- 8 ounces smoked Gouda, shredded (about 2 cups)
- 1 tablespoon unsalted butter, softened, for the dish
- 1 teaspoon fresh thyme leaves, for garnish (optional)
- ¼ teaspoon flaky sea salt, for finishing (optional)
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Steps
- Infuse the cream: In a medium saucepan, combine the heavy cream, milk, smashed garlic, thyme sprigs, rosemary sprig, bay leaf, nutmeg, salt, and pepper. Warm over medium-low heat just until you see the first lazy bubbles at the edge of the pan — do not let it boil — then remove from the heat, cover, and let it steep for 20 minutes so the garlic and herbs perfume the cream. Strain through a fine-mesh sieve into a bowl, pressing gently on the solids, and discard the aromatics.
- Prep the oven and dish: While the cream steeps, position a rack in the center of the oven and preheat to 375°F. Generously butter a 9x13-inch (3-quart) baking dish.
- Slice the sweet potatoes: Peel the sweet potatoes and slice them crosswise into very thin, even rounds — a scant ⅛ inch thick. A mandoline makes this fast and uniform, but a sharp chef's knife and a steady hand work too. The thinness is the whole game here: thicker slices will leave raw, hard centers while the top overbrowns.
- Layer the gratin: Arrange one third of the sweet potato slices in the dish, shingling them in slightly overlapping rows. Scatter with one third of the smoked Gouda. Repeat twice more — potatoes, then Gouda — finishing with a layer of cheese on top. Gently press down with your palms so the slices settle and sit level.
- Pour and bake: Pour the strained herb cream evenly over the top, letting it settle into the layers. Cover the dish tightly with foil and bake for 30 minutes so the potatoes steam and soften.
- Finish uncovered: Remove the foil and continue baking until the top is deeply golden and burnished, the cream is bubbling thickly, and a paring knife slides into the center with no resistance, 25 to 35 minutes more. The gratin is done when an instant-read thermometer inserted into the center reads 185°F — the temperature where the sweet potato starch has fully softened. Watch the cheese: smoked Gouda melts at about 150°F and will turn grainy if overheated, so pull it as soon as the potatoes are tender rather than chasing a darker top.
- Rest and serve: Let the gratin rest for 10 to 15 minutes so the cream sets and the layers slice cleanly. Scatter with fresh thyme leaves and a pinch of flaky sea salt, if you like, and serve hot.
Tips & Variations
Make Ahead
This gratin is built for the make-ahead holiday shuffle. Assemble it completely up to 1 day ahead — layer the potatoes and Gouda, but hold the cream in a covered container in the fridge — then cover the dish and refrigerate. When you're ready, pour the reserved cream over the top, let the dish sit at room temperature for 30 minutes, and bake as directed, adding about 10 minutes to the covered bake since it's starting cold. You can also bake it fully up to 2 days ahead: cool, cover, and refrigerate, then reheat covered in a 350°F oven for 25 to 30 minutes until hot through, uncovering for the last 5 minutes to refresh the top.
Storage
Refrigerate leftovers in an airtight container for up to 4 days. Reheat individual portions in the microwave or a covered dish in a 350°F oven until hot through. The gratin freezes well for up to 2 months — cool completely, wrap tightly, and freeze; thaw overnight in the fridge and reheat covered so the cream doesn't dry out. Note that the smoked Gouda's texture is at its best fresh, so reheating gently (not boiling) keeps it from turning grainy.
Substitutions
Swap the smoked Gouda for regular Gouda, Fontina, or Gruyère — all are low-moisture melting cheeses that behave the same way; a mix of Gouda and Gruyère is especially nice. Prefer a sharper top? Finish with a sprinkle of Parmesan in place of some of the Gouda. Trade the thyme and rosemary for sage, which loves both sweet potato and smoked cheese. To lighten it, replace up to half the cream with whole milk or half-and-half (the custard will set a touch looser). For a dairy-free version, this recipe isn't a natural fit — the cream is load-bearing — but you can use full-fat coconut milk and a good melting vegan smoked cheese, watching the bake closely since coconut milk browns faster. If you only have russet or Yukon Gold potatoes, our <a href="/potatoes-dauphinoise/">Potatoes Dauphinoise</a> is the better-tested route.
Nutrition
Per serving: ⅛ of the recipe
Reviews
Reviews coming soon! In the meantime, let us know what you think of this recipe.
