Creamy Sweet Potato Gratin with Yukon Gold potatoes, Gruyère, and Parmesan cheese baked to a golden, tender perfection. This easy potato gratin features layers of thinly sliced sweet and yellow potatoes with garlic, thyme, and a rich half-and-half sauce. Perfect for holiday dinners, family meals, or weeknight side dishes.

Ingredients

700 g (1½ lb) red-skinned sweet potatoes, peeled and sliced
450 g (1 lb) Yukon Gold potatoes, peeled and sliced
360 ml (1½ cups) half-and-half
1½ tablespoons butter, divided
1 teaspoon minced garlic
1 tablespoon fresh thyme, chopped
½ teaspoon fine sea salt, or to taste
Freshly ground black pepper, to taste
150 g (1½ cups) shredded Gruyère cheese
25 g (¼ cup) finely shredded Parmesan cheese

Instructions

Slice the potatoes
Using a mandoline or food processor, slice the sweet potatoes and Yukon Gold potatoes into 3 mm (⅛-inch) rounds.
Prepare the cream mixture
In a small saucepan over low heat, combine the half-and-half, 1 tablespoon of butter, and minced garlic. Warm gently, making sure it doesn’t boil over.
Preheat and butter the dish
Preheat the oven to 200°C (400°F). Butter a 30 cm (12-inch) cast iron pan, gratin dish, or similar-sized baking dish with the remaining ½ tablespoon of butter.
Layer the potatoes
Arrange half of the potato slices in the dish, alternating sweet potato and Yukon Gold slices. Sprinkle with half of the salt, black pepper, thyme, and half of the Gruyère and Parmesan cheese.
Repeat the layers
Layer the remaining potatoes, salt, pepper, thyme, and cheeses. Gently press the layers down with your hands and pour the warm half-and-half mixture evenly over the top.
Bake the gratin
Cover the dish (with foil or a lid) and bake for 40 minutes. Remove the cover and bake for an additional 15 minutes, or until the top is golden brown, the potatoes are tender, and most of the liquid is absorbed.
Rest before serving
Allow the gratin to rest for 5–10 minutes before serving to let it set.

Why You’ll Love This Recipe

Combines the natural sweetness of sweet potatoes with creamy cheese
Elegant side dish suitable for weeknight dinners or holiday meals
Crispy, golden top with tender, flavorful layers underneath
Uses simple ingredients found in most kitchens

Tips

Slice potatoes evenly for uniform cooking.
Warm the cream gently to avoid boiling over and curdling.
Let the gratin rest before serving to make slicing easier.

Variations and Substitutions

Cheese swap: Use Fontina, cheddar, or mozzarella instead of Gruyère.
Dairy-free: Use plant-based milk and vegan cheese alternatives.
Herbs: Replace thyme with rosemary, sage, or parsley for different flavors.
Add-ins: Layer in caramelized onions or cooked bacon for extra richness.

FAQs

Can I make this ahead of time?
Yes, assemble the gratin and refrigerate for up to 24 hours before baking. Increase baking time slightly if baking straight from the fridge.

Can I use only sweet potatoes or only Yukon Gold?
Yes, but mixing them adds both color and flavor contrast.

How do I store leftovers?
Cover tightly and refrigerate for up to 3 days. Reheat in the oven for best results.

Serving

Serve as a side dish with roasted meats, poultry, or vegetarian mains. Perfect for Thanksgiving, Christmas, or any family dinner.

Suggestions

Sprinkle extra Parmesan on top for a crispier crust.
Drizzle with a little olive oil before baking for added richness.
Pair with a simple green salad to balance the creamy gratin.