Sweet Potato Au Gratin (Creamy and Cheesy Holiday Side) Recipe
Sweet Potato Au Gratin is a creamy, cheesy holiday side dish featuring thinly sliced sweet potatoes layered with a rich mixture of heavy cream, garlic, fresh thyme, and three kinds of cheese: Gruyere, Gouda, and Parmesan. Baked to golden perfection, this comforting casserole is perfect for festive occasions and family meals.
- Prep Time: 15 minutes
- Cook Time: 60 minutes
- Total Time: 75 minutes
- Yield: 12 servings
- Category: Side Dish
- Method: Baking
- Cuisine: American
Ingredients
Sweet Potatoes
- 3 sweet potatoes, sliced 1/8 inch thick (using mandolin slicer)
Cheese Mixture
- 1 1/2 cups Gruyere cheese, shredded
- 1/2 cup Gouda cheese, shredded
- 1/2 cup Parmesan cheese, shredded
Cream Sauce
- 1 3/4 cups heavy cream
- 4–5 cloves garlic, minced
- 2 tbsp unsalted butter, melted
- 2 tbsp fresh thyme
- Salt and pepper, to taste
Instructions
- Preheat the oven: Preheat your oven to 375°F (190°C) to prepare for baking the casserole.
- Prepare the cream sauce: In a saucepan over medium heat, melt the butter. Add the minced garlic and cook for 1-2 minutes until fragrant. Pour in the heavy cream, then season with salt and pepper. Heat the mixture gently for a couple of minutes. It won’t thicken much now but will thicken during baking due to the potato starch.
- Layer the sweet potatoes: Grease a baking dish, then layer the sliced sweet potatoes evenly. After adding each layer, season with salt, pepper, and fresh thyme, followed by sprinkling a mix of Gruyere, Gouda, and Parmesan cheeses. Repeat to create 3-4 layers.
- Add cream sauce: Pour the prepared cream mixture over each layer evenly, making sure the potatoes are well coated but not overloaded.
- Top with cheese: Sprinkle the remaining cheese mixture over the top layer of potatoes for a golden, cheesy crust.
- Bake covered: Cover the baking dish with aluminum foil and bake for about 45 minutes, allowing the potatoes to cook through and the sauce to thicken.
- Bake uncovered: Remove the foil and bake for an additional 15-20 minutes until the sweet potatoes are tender, and the top is bubbling and golden brown.
Notes
- Using a mandolin slicer ensures even, thin slices which cook uniformly.
- Do not add too much cream on each layer to avoid a soupy casserole; layering the cream evenly helps with texture.
- Covering the dish during the first part of baking traps moisture, helping the potatoes cook through without drying out.
- Fresh thyme adds a subtle herbaceous flavor that complements the sweetness of the potatoes and richness of the cheeses.
- This dish can be prepared ahead and refrigerated before baking to save time on the day of serving.
