Cheesy Sweet Potato Gratin (Printable)
Sweet potatoes and caramelized onions baked with melted cheese in a rich, creamy gratin.
# What You’ll 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 or all-purpose flour for thickening
14 - 2 tbsp chopped fresh chives for garnish
# Steps:
01 - Preheat 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 minced garlic and cook for 1 minute more. Remove from heat.
03 - In a small saucepan, combine heavy cream, whole milk, dried thyme, ground nutmeg, black pepper, and remaining 1 tbsp butter. Heat over medium-low heat until steaming, do not boil. If using flour, whisk in until smooth to slightly thicken the mixture.
04 - Arrange half of the sweet potato slices in the prepared baking dish, overlapping slightly. Season lightly with salt.
05 - Spread half of the caramelized onions over the potatoes. Sprinkle with half of the Gruyère and half of the cheddar cheese.
06 - Repeat with remaining sweet potato slices, caramelized onions, and cheeses.
07 - Pour the warm cream mixture evenly over the layered ingredients, ensuring it distributes throughout the dish.
08 - Cover the baking dish tightly with aluminum foil. Bake for 40 minutes.
09 - Remove the foil and bake uncovered for an additional 20 minutes, or until the top is golden brown and the potatoes are fork-tender.
10 - Let the gratin rest for 10 minutes before serving to allow the layers to set. Garnish with fresh chopped chives if desired.
# Expert Advice:
01 -
- The combination of sweet potatoes and savory onions hits that perfect balance between sweet and salty that makes everyone go back for seconds
- Its the kind of dish that makes people think you spent hours in the kitchen, but the active prep time is surprisingly manageable
02 -
- Sweet potatoes vary wildly in thickness, so the cooking time might need adjustment—test with a fork in several spots
- The cream mixture might look like too much liquid initially, but trust the process as it creates that luscious sauce
03 -
- Don't rush the onion caramelization—those 25 minutes of patience transform sharp raw onions into something sweet and complex
- If the top browns too quickly, loosely tent with foil for the last 10 minutes of baking