Cheesy Sweet Potato Gratin (Printable)
Layers of sweet potatoes, caramelized onions, and cheese baked to a golden, creamy finish.
# 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
13 - 1 tbsp all-purpose flour for thickening
14 - 2 tbsp chopped fresh chives for garnish
# How to Make It:
01 - Preheat oven to 375°F. Grease a 9x13-inch baking dish with butter or cooking spray.
02 - Melt 2 tbsp butter in a large skillet over medium heat. 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, but do not boil. If using flour for thickening, whisk it in until smooth.
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 reaches all corners of the dish.
08 - Cover the baking dish tightly with aluminum foil. Bake for 40 minutes.
09 - Remove foil and continue baking uncovered for an additional 20 minutes, or until the top is golden brown and bubbly, and potatoes are fork-tender.
10 - Let the gratin rest for 10 minutes before serving to allow the layers to set. Garnish with fresh chives if desired.
# Expert Advice:
01 -
- The sweet and savory balance is absolutely addictive and keeps people coming back for seconds
- It can be assembled ahead of time which is a lifesaver when hosting dinner parties
02 -
- Slicing potatoes evenly with a mandoline or sharp knife is crucial because uneven slices mean some pieces will be undercooked while others turn to mush
- Letting the gratin rest for 10 minutes after baking allows the sauce to thicken slightly so it does not run all over the plate when you serve it
03 -
- Sprinkle a little extra cheese on top during the last 5 minutes if you want an extra-crispy, golden crust
- Grating the cheese yourself instead of buying pre-shredded makes a huge difference in how smoothly it melts