Easy Sweet Potato Gratin is a simple, comforting dish that brings together tender slices of sweet potatoes baked in a creamy, cheesy sauce. It’s creamy, slightly sweet, and has just the right amount of gooey melted cheese on top that gets golden and crispy as it bakes. This dish feels like a warm hug on a plate and is a perfect side for any cozy dinner.
I love making this gratin when I want something that feels special but doesn’t take forever in the kitchen. The best part is how easy it is—just layer up the potatoes, pour on the creamy sauce, sprinkle cheese, and pop it in the oven. I always find it’s a big hit, whether it’s for a family dinner or a holiday meal, and people often ask for seconds after tasting it!
My favorite way to serve this sweet potato gratin is alongside roasted chicken or a simple green salad to balance all that richness. It’s one of those dishes that warms you up and makes your home smell amazing. If you’re new to gratins, this recipe is a great place to start because it feels fancy but comes together super easily.
Key Ingredients & Substitutions
Sweet Potatoes: These are the star of the dish with their natural sweetness and creamy texture when baked. Choose firm, bright orange ones for best flavor. If you want, you can mix in some Yukon gold potatoes for a milder taste.
Cream & Milk: The combo creates a rich, silky sauce. Heavy cream makes it extra creamy, but you can use half-and-half or whole milk for a lighter version. Just expect a less thick sauce.
Cheese: Gruyère is ideal here for its melting quality and nutty flavor. Sharp white cheddar also works well and adds a bit more tang. If you want a dairy-free option, try vegan cheese blends designed for melting.
Herbs & Seasoning: Fresh thyme gives a lovely earthy note. If you don’t have thyme, rosemary or sage are nice substitutes. Salt and pepper balance the sweetness and richness perfectly.
How Do I Get Thin, Even Sweet Potato Slices for a Smooth Gratin?
Thin slices cook more evenly and help the cream soak through the layers. Here’s how I slice mine:
- Use a sharp knife or, better yet, a mandoline slicer for uniform, paper-thin slices.
- Peel the sweet potatoes first for a smooth texture, but you can leave the skin on if you like it rustic.
- Take your time layering them slightly overlapping to create a nice, even surface that cooks through well.
Thinner slices mean the gratin cooks quicker and the flavors blend better—avoiding any undercooked or mushy spots!
Equipment You’ll Need
- Mandoline slicer – it helps you slice sweet potatoes thin and even without much effort.
- Medium saucepan – perfect for gently warming the cream and milk mixture.
- 8×8-inch baking dish – just the right size for layering and baking the gratin evenly.
- Aluminum foil – covers the dish while baking to keep moisture in and prevent the top from burning.
- Sharp knife – great for trimming and prepping sweet potatoes if you don’t have a mandoline.
Flavor Variations & Add-Ins
- Add cooked crumbled sausage for a meaty, savory twist that pairs well with the creamy potatoes.
- Mix in caramelized onions between layers to add sweetness and a rich, mellow flavor.
- Swap Gruyère cheese for mozzarella or fontina for a milder, creamier melt.
- Stir in fresh sage or rosemary for an herbal note that complements the natural sweetness of the potatoes.
Easy Sweet Potato Gratin
Ingredients You’ll Need:
For the Gratin:
- 3 large sweet potatoes, peeled and thinly sliced
- 1 cup heavy cream
- 1 cup whole milk
- 2 cloves garlic, minced
- 1 ½ cups shredded Gruyère or sharp white cheddar cheese
- 2 tablespoons unsalted butter, softened
- 1 teaspoon fresh thyme leaves (plus extra sprigs for garnish)
- Salt and freshly ground black pepper, to taste
For Serving (Optional):
- Mixed salad greens
How Much Time Will You Need?
Total time is about 1 hour, including 10-15 minutes prep time and 45-55 minutes baking. You’ll also want to let the dish rest for about 5-10 minutes before serving to help it set.
Step-by-Step Instructions:
1. Preheat and Prepare
Start by preheating your oven to 375°F (190°C). Butter a medium baking dish (about 8×8 inches) so the gratin won’t stick and will bake evenly.
2. Make the Cream Mixture
In a saucepan, combine the heavy cream, milk, minced garlic, and fresh thyme leaves. Warm the mixture over medium heat just until it starts to simmer, then take it off the heat to keep the flavors fresh.
3. Layer the Sweet Potatoes
Lay a single layer of sweet potato slices in the bottom of your prepared dish. Overlap slices just a little to cover the surface fully.
4. Season and Cheese
Sprinkle salt and pepper over the potatoes. Then add a light handful of shredded cheese evenly across the layer. Pour a small amount of the warm cream mixture over everything to help it soak in and get creamy.
5. Repeat the Layers
Keep layering sweet potatoes, seasoning, cheese, and cream until all the ingredients are used up. Finish with a strong layer of cheese on top for a golden finish.
6. Bake Covered
Cover the dish with aluminum foil and bake for about 30 minutes. This helps the potatoes soften with steam and keeps the moisture locked in.
7. Bake Uncovered Until Golden
Remove the foil and bake uncovered for an additional 20-25 minutes. This step browns the cheese and crisps the edges to perfection. The sweet potatoes should be tender when pierced with a fork.
8. Let Rest and Serve
Take the gratin out of the oven and let it rest for 5-10 minutes so it can set and become easier to cut. Garnish with fresh thyme sprigs, and serve alongside a fresh green salad for a complete meal.
Can I Use Frozen Sweet Potato Slices?
Yes, you can use frozen sweet potato slices, but make sure to thaw them completely and pat them dry to remove excess moisture before layering. This helps prevent the gratin from becoming watery.
How Do I Store Leftovers?
Store any leftovers in an airtight container in the fridge for up to 3 days. Reheat gently in the oven or microwave until warmed through for best texture.
Can I Make This Gratin Ahead of Time?
Absolutely! Assemble the gratin and keep it covered in the fridge for up to 24 hours before baking. You might need to add a few extra minutes to the baking time if cooking straight from the fridge.
What Can I Substitute for Gruyère Cheese?
If you don’t have Gruyère, try sharp white cheddar, fontina, or mozzarella for a deliciously melty alternative that still gives great flavor.