Easy Sweet Potato Gratin is a simple, comforting dish that brings together tender slices of sweet potato layered with creamy cheese and a touch of garlic. It’s a great way to turn those sweet potatoes into a cheesy, golden side that feels fancy but is actually really easy to make.
I love making this gratin when I want something cozy but don’t want to spend hours in the kitchen. The best part is watching the cheese bubble up and the edges turn perfectly crispy while the sweet potatoes stay soft and flavorful. It’s one of those dishes that feels like a special treat but doesn’t need a complicated recipe or fancy ingredients.
My favorite way to serve this is alongside a simple roast chicken or a fresh green salad to balance out the richness. It’s also a crowd-pleaser at dinner parties or holiday meals because it combines sweet, creamy, and cheesy all in one bite. I always keep a note to make extra because it tastes even better the next day!
Key Ingredients & Substitutions
Sweet Potatoes: Using firm, large sweet potatoes works best. Thin slices help them cook evenly and absorb cream and cheese flavors. If you prefer, you can mix in some regular potatoes for a different texture.
Heavy Cream: Heavy cream creates that rich, creamy texture. For a lighter option, try half-and-half or whole milk, but the gratin won’t be quite as creamy.
Gruyère Cheese: Gruyère melts beautifully and adds a mild nutty flavor. Sharp cheddar is a good substitution if you want a stronger cheese taste, or use mozzarella for a milder, stretchy texture.
Garlic & Thyme: Fresh garlic and thyme brighten the gratin’s richness. If fresh thyme isn’t available, dried thyme works fine. For garlic, you can increase the quantity if you love its flavor.
Parmesan Cheese: Parmesan adds a nice sharpness and helps form the golden crust on top. Pecorino Romano is a good alternative, providing a bit more saltiness.
How Can I Get Thin, Even Sweet Potato Slices for My Gratin?
Getting thin slices is key for even baking. Here’s how I do it:
- Use a sharp kitchen knife or better, a mandoline slicer set to about 1/8 inch. Be careful with mandolines—use a safety guard!
- If slicing by hand, take your time and try to keep slices the same thickness so all cook evenly.
- Peeling the sweet potatoes before slicing ensures smooth layers and creaminess in each bite.
- If you want to save time, some stores sell pre-sliced sweet potatoes—these work well too, just check thickness.
Equipment You’ll Need
- Mandoline slicer – Makes slicing sweet potatoes thin and even quick and safe if you use the guard.
- Medium baking dish (8×8 inches) – Perfect size for layering and baking the gratin evenly.
- Small saucepan – Warm the cream with garlic and thyme gently without boiling.
- Sharp knife – Handy if you slice the sweet potatoes by hand instead of a mandoline.
- Aluminum foil – To cover the gratin while baking, so it cooks through without drying out.
Flavor Variations & Add-Ins
- Swap Gruyère for sharp cheddar or mozzarella for a different cheese flavor and texture.
- Add cooked bacon or pancetta between layers for a smoky, salty boost.
- Mix in thin slices of apple or pear for a touch of sweet freshness with the potatoes.
- Stir fresh sage or rosemary into the cream to add earthy herbal notes that pair well with sweet potatoes.
Easy Sweet Potato Gratin
Ingredients You’ll Need:
For the Gratin:
- 3 large sweet potatoes, peeled and thinly sliced (about 1/8 inch thick)
- 1 1/2 cups heavy cream
- 1 garlic clove, minced
- 1 cup grated Gruyère cheese (or sharp cheddar as an alternative)
- 1/2 cup grated Parmesan cheese
- 1 tsp fresh thyme leaves (or 1/2 tsp dried thyme)
- Salt and freshly ground black pepper, to taste
- 1 tbsp unsalted butter, for greasing the baking dish
- Fresh parsley or additional thyme, chopped, for garnish
How Much Time Will You Need?
This sweet potato gratin takes about 15 minutes of preparation and roughly 50-55 minutes baking time, including a covered bake followed by browning. Plan for about 10 minutes extra to let it rest before serving, so in total, about 1 hour and 15 minutes.
Step-by-Step Instructions:
1. Prepare the Oven and Baking Dish:
Preheat your oven to 375°F (190°C). Grease a medium baking dish (about 8×8 inches) with the butter to prevent sticking.
2. Infuse the Cream:
In a small saucepan, warm the heavy cream gently with the minced garlic and thyme. Keep the cream just warm—don’t let it boil. Remove from the heat and let it sit for 5 minutes to absorb the flavors.
3. Layer the Sweet Potatoes:
Arrange a single layer of sweet potato slices in the greased baking dish, overlapping them slightly. Sprinkle a bit of salt, pepper, and some of the Gruyère cheese over this layer. Pour a small amount of the warm cream over the potatoes, just enough to moisten them.
4. Repeat Layers:
Keep layering sweet potatoes, seasoning, cheese, and cream until all ingredients are used, finishing with a cheese layer on top. Sprinkle the Parmesan evenly over the last layer for a nice crunchy crust.
5. Bake Covered:
Cover the dish with aluminum foil tightly and bake for 30 minutes. This helps the potatoes cook through evenly.
6. Bake Uncovered to Brown:
Remove the foil and bake for another 20-25 minutes, or until the top is golden brown, bubbly, and the sweet potatoes are tender when pierced with a fork.
7. Rest and Garnish:
Allow the gratin to rest for 5-10 minutes—this makes it easier to cut and serve. Just before serving, sprinkle freshly chopped parsley or thyme on top for a fresh touch.
Enjoy this comforting, creamy sweet potato gratin warm, served with a crisp green salad or alongside your favorite protein.
Can I Use Frozen Sweet Potatoes for This Gratin?
Yes, but thaw them completely and pat dry before using. Frozen sweet potatoes hold more moisture, so drying 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, covering loosely to keep moisture in.
Can I Make This Gratin Ahead of Time?
Absolutely! Assemble the gratin and cover it; keep it refrigerated for up to 24 hours before baking. Add a few extra minutes to the baking time if baking straight from cold.
What Cheese Can I Substitute if I Don’t Have Gruyère?
Sharp cheddar is a great substitute that melts well and adds flavor. Mozzarella can also work for a milder taste, but it won’t give the same nuttiness as Gruyère.
