Cheesy Sweet Potato Gratin (Printable)
Comforting gratin with layered sweet potatoes, caramelized onions, and a blend of melted cheeses.
# What You Need:
→ Vegetables
01 - 2 lbs sweet potatoes, peeled and thinly sliced
02 - 2 large yellow onions, thinly sliced
03 - 2 cloves garlic, minced
→ Dairy & Cheese
04 - 2 cups shredded Gruyère cheese
05 - 1 cup shredded sharp cheddar cheese
06 - 1 1/2 cups heavy cream
07 - 1/2 cup whole milk
08 - 3 tbsp unsalted butter
→ Seasonings
09 - 1/2 tsp dried thyme
10 - 1/2 tsp ground black pepper
11 - 1/2 tsp salt plus more to taste
12 - 1/4 tsp ground nutmeg
→ Optional Additions
13 - 1 tbsp gluten-free flour or all-purpose flour for thickening
14 - 2 tbsp chopped fresh chives for garnish
# How To Make It:
01 - Preheat your oven to 375°F. Grease a 9x13-inch baking dish with butter or cooking spray.
02 - In a large skillet over medium heat, melt 2 tbsp butter. Add sliced onions and a pinch of salt. Cook, stirring frequently, until onions are deeply golden and caramelized, about 20-25 minutes. Add garlic and cook for 1 minute more. Remove from heat.
03 - In a small saucepan, heat cream, milk, thyme, nutmeg, black pepper, and remaining 1 tbsp butter over medium-low heat until steaming but not boiling. If using flour, whisk it in until smooth to slightly thicken the mixture.
04 - Arrange half of the sweet potato slices in the prepared baking dish. Season lightly with salt. Spread half of the caramelized onions over the potatoes. Sprinkle with half of the Gruyère and cheddar cheese.
05 - Repeat with remaining sweet potato slices, onions, and cheeses to create a second complete layer.
06 - Pour the warm cream mixture evenly over the layered ingredients, ensuring it reaches all corners of the dish.
07 - Cover the baking dish tightly with aluminum foil. Bake for 40 minutes to allow potatoes to cook through.
08 - Remove the foil and continue baking uncovered for an additional 20 minutes, until the top is golden brown and the potatoes are fork-tender.
09 - Let the gratin rest for 10 minutes before serving to allow the layers to set. Garnish with fresh chives if desired.
# Expert Suggestions:
01 -
- The caramelized onions become like candy, balancing the rich cheese sauce perfectly
- It makes enough for a crowd but somehow tastes even better as leftovers the next day
02 -
- Sweet potatoes release more moisture than regular potatoes, so the sauce might look thinner than expected during baking. It thickens as it rests.
- Overbaking is better than underbaking here. Undercooked sweet potatoes have an unpleasant texture.
03 -
- Use a mandoline if you have one. The slices will be impossibly even and cook uniformly.
- Season each layer lightly with salt rather than dumping it all on top. This ensures even seasoning throughout.