Cheesy Sweet Potato Gratin (Printable)
Rich gratin with sweet potatoes, caramelized onions, and a blend of cheeses baked until golden.
# What goes in:
→ 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 gluten-free or all-purpose flour for thickening
14 - 2 tbsp chopped fresh chives for garnish
# Directions:
01 - Preheat oven to 375°F and generously grease a 9x13-inch baking dish with butter or cooking spray.
02 - Melt 2 tablespoons 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 during the last minute and remove from heat.
03 - In a small saucepan, combine heavy cream, whole milk, dried thyme, nutmeg, black pepper, and remaining 1 tablespoon butter. Heat over medium-low until steaming but not boiling. If using flour for thickening, whisk it in until smooth and slightly thickened. Remove from heat.
04 - Arrange half of the sweet potato slices in an even layer at the bottom of the prepared baking dish. 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 - Add remaining sweet potato slices, followed by remaining caramelized onions, and finish with remaining cheeses.
07 - Evenly pour the warm cream mixture over the layered ingredients, ensuring coverage across the entire dish.
08 - Cover the baking dish tightly with aluminum foil and bake for 40 minutes.
09 - Remove foil and continue baking uncovered for 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 layers to set. Garnish with fresh chives if desired.
# Expert Advice:
01 -
- The combination of sweet potatoes and caramelized onions creates an incredible sweet and savory balance that feels sophisticated but comforting
- This gratin works as both a stunning holiday side dish or a cozy main course with a simple green salad
02 -
- Resist the urge to rush the caramelized onions, because that concentrated sweetness is what makes this dish memorable
- Slicing potatoes thinly and evenly is crucial, so use a mandoline if you have one or take your time with a sharp knife
03 -
- Place your baking dish on a rimmed baking sheet to catch any bubbles that might spill over in the oven
- Grating your own cheese instead of buying pre-shredded makes a noticeable difference in how smoothly it melts