When the cooler months arrive, comfort food takes center stage at the dinner table. There’s nothing more inviting than the aroma of a bubbling gratin fresh from the oven, its golden crust promising warmth and satisfaction. This Creamy Sweet Potato and Spinach Gratin is the perfect dish to serve on a cozy autumn evening, during festive holiday gatherings, or even as a hearty side for a weekend family dinner. It strikes the ideal balance between indulgence and nourishment, showcasing layers of velvety sweet potatoes, earthy spinach, and a luscious cream sauce that ties everything together.
The inspiration for this dish comes from classic French gratins, which are often rich and buttery. Here, we put a wholesome twist on tradition by introducing sweet potatoes for their natural sweetness and nutrients, alongside fresh spinach for a burst of color and flavor. The result is a gratin that feels both luxurious and nourishing—a dish that can take center stage at your table or complement a variety of mains.
Why You’ll Love This Recipe
This gratin isn’t just another side dish—it’s a recipe you’ll return to again and again. Here’s why:
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Perfect Balance of Flavors: The sweetness of the potatoes meets the subtle bitterness of spinach and the richness of the creamy sauce.
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Wholesome Yet Comforting: Packed with vitamins A and C, fiber, and iron, this dish nourishes while still tasting indulgent.
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Versatile: Serve it as a vegetarian main with a crisp salad, or as a side dish to roasted chicken, turkey, or beef.
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Make-Ahead Friendly: Assemble it in advance and bake just before serving—ideal for busy weeknights or holiday prep.
Ingredients
To make this delicious gratin, you’ll need simple yet flavorful ingredients that come together beautifully.
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3 large sweet potatoes, peeled and thinly sliced
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3 cups fresh spinach (or 2 cups frozen, thawed and drained well)
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2 tablespoons unsalted butter
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2 tablespoons all-purpose flour
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2 cups whole milk (or half-and-half for extra richness)
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1 cup heavy cream
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2 garlic cloves, minced
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1 teaspoon fresh thyme (or ½ teaspoon dried thyme)
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½ teaspoon ground nutmeg
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1 cup grated Gruyère cheese (or substitute with Swiss or sharp white cheddar)
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½ cup grated Parmesan cheese
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Salt and black pepper to taste
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Olive oil for greasing
Directions
1. Prepare the Sweet Potatoes
Start by peeling the sweet potatoes and slicing them into thin, uniform rounds, about ⅛-inch thick. This step is crucial because the evenness of the slices determines how well the layers cook together in the gratin. Too thick, and the potatoes may remain firm in the middle; too thin, and they could break apart. A sharp knife works fine, but if you own a mandoline slicer, this is the perfect time to use it. It guarantees consistent slices and saves time. Once sliced, place the sweet potatoes in a bowl of cold water to prevent oxidation, which can cause browning. Keeping them in water also washes away some excess starch, which helps maintain clean, separate layers in the gratin.
2. Cook the Spinach
While the sweet potatoes rest, move on to the spinach. If you’re using fresh spinach, give it a quick sauté in a skillet with a drizzle of olive oil. It only takes 2–3 minutes over medium heat for the leaves to wilt down. You don’t want to overcook them since they’ll continue to cook in the oven. If you’re using frozen spinach, make sure it’s fully thawed before adding it to the dish. Once thawed, squeeze out as much liquid as possible using your hands or by pressing the spinach in a clean kitchen towel. Excess water can make the gratin runny, so this step is essential for achieving the creamy texture we’re aiming for.
3. Make the Creamy Sauce
The sauce is the heart of this gratin, transforming the layers of vegetables into something decadent and satisfying. Begin by melting butter in a medium saucepan over medium heat. Once melted, add the flour and whisk continuously for about 1–2 minutes to create a smooth roux. This process cooks out the raw flour taste and lays the foundation for a rich, velvety sauce. Gradually pour in the milk and cream, whisking constantly to avoid lumps. You’ll notice the sauce beginning to thicken after 5–7 minutes of gentle stirring. At this point, stir in minced garlic, thyme, nutmeg, and a generous pinch of salt and pepper. These seasonings infuse the sauce with warmth and depth. Finally, remove the pan from heat and fold in half of the Gruyère cheese, which melts beautifully and adds a subtle nuttiness.
4. Assemble the Gratin
Preheat your oven to 375°F (190°C) and lightly grease a baking dish with olive oil. To assemble, begin with a single layer of sweet potato slices on the bottom of the dish, overlapping them slightly like shingles on a roof. Add a layer of spinach on top, then spoon over a portion of the creamy sauce, making sure it seeps between the layers. Continue layering in this fashion—sweet potatoes, spinach, sauce—until all the ingredients are used. The final layer should be sweet potatoes, which creates a neat, structured top. Pour the remaining sauce evenly across the surface to ensure every bite is coated in creaminess.
5. Add the Topping
Now comes the finishing touch. Sprinkle the remaining Gruyère cheese and all of the Parmesan evenly over the top layer. As the gratin bakes, this cheesy topping will melt, bubble, and turn golden brown, forming a crust that contrasts beautifully with the tender layers underneath. The Parmesan adds a salty, savory sharpness that balances the natural sweetness of the potatoes.
6. Bake
Cover the baking dish with foil to trap steam and encourage the potatoes to cook through without drying out. Place it in the oven and bake for about 30 minutes. After this initial bake, remove the foil and continue cooking for another 20–25 minutes. This uncovered time allows the cheese topping to brown and crisp while the sauce thickens and bubbles. You’ll know the gratin is done when the potatoes are fork-tender and the top is beautifully golden. Once baked, resist the urge to dig in immediately—let the dish rest for at least 10 minutes. This short waiting period allows the layers to set, making it easier to slice and serve neat portions.
Tips for Success
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Thin and Even Slices: Uniform sweet potato slices ensure even cooking.
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Drain Spinach Thoroughly: Excess moisture can make the dish watery—squeeze out as much liquid as possible.
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Season Every Layer: Lightly season each layer of sweet potatoes and spinach to maximize flavor.
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Rest Before Serving: Giving the gratin a few minutes to settle makes slicing cleaner and enhances the texture.
Variations to Try
Cheesy Upgrade
Add a layer of mozzarella between the sweet potatoes and spinach for extra gooeyness.
Add Protein
Include cooked chicken, turkey, or ham between the layers to make this gratin a hearty one-pan meal.
Vegan Version
Swap the butter for olive oil, use plant-based milk and cream, and replace the cheese with a dairy-free alternative. Nutritional yeast can also boost the cheesy flavor.
Spice It Up
Add a pinch of smoked paprika or cayenne pepper to the cream sauce for a gentle heat that complements the sweet potatoes.
Mediterranean Twist
Layer in caramelized onions, sun-dried tomatoes, and a sprinkle of feta cheese for a bright, tangy variation.
What to Serve With Sweet Potato and Spinach Gratin
This dish is versatile and pairs beautifully with many mains:
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Holiday Roasts: Turkey, beef, or lamb make festive companions.
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Weeknight Favorites: Serve alongside baked chicken, salmon, or pork chops.
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Vegetarian Meal: Pair with a fresh arugula salad and crusty bread for a balanced dinner.
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Comfort Pairings: Serve with roasted root vegetables, steamed green beans, or a hearty soup.
Make-Ahead and Storage Tips
Make-Ahead
Assemble the gratin up to a day in advance, cover tightly with foil, and refrigerate. Bake when ready to serve, adding an extra 10 minutes of cook time if chilled.
Freezing
Bake the gratin, let it cool completely, and wrap tightly in foil. Freeze for up to 3 months. Reheat covered in the oven at 350°F (175°C) until warmed through.
Storing Leftovers
Refrigerate leftovers in an airtight container for up to 4 days. Reheat individual portions in the microwave or oven.
Nutritional Benefits
Sweet potatoes aren’t just delicious—they’re a nutritional powerhouse. They’re packed with beta-carotene (a precursor to vitamin A), fiber, and antioxidants that support immune function and eye health. Spinach brings iron, folate, and vitamin K to the table, while the milk and cheese provide calcium and protein. Together, these ingredients create a dish that feels indulgent but is also full of goodness.
Serving Ideas for Special Occasions
This gratin shines during the holidays. Place it at the center of your Thanksgiving spread, serve it at Christmas alongside roasted meats, or bring it to a potluck to wow your friends. It’s elegant enough for celebrations but simple enough for a weeknight treat.
For family-style dining, add it to the table with roasted vegetables and a loaf of fresh bread. The possibilities are endless.
Frequently Asked Questions
1. Can I use regular potatoes instead of sweet potatoes?
Yes, but the flavor profile will change. Regular potatoes offer a more neutral base, while sweet potatoes add natural sweetness and depth.
2. Can I use frozen spinach?
Absolutely. Just make sure to thaw it completely and squeeze out as much water as possible to avoid excess liquid in the dish.
3. What’s the best cheese for this recipe?
Gruyère melts beautifully and adds nutty richness, but you can also use Swiss, white cheddar, or even mozzarella for a milder flavor.
4. How do I know when the gratin is done?
The sweet potatoes should be fork-tender, and the top should be golden and bubbly. Resting the dish for 10 minutes before serving will also ensure perfect layers.
