Cheesy Sweet Potato Gratin (Printable)
Layers of sweet potatoes, caramelized onions, and melted cheese baked to golden perfection.
# 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 - 1½ cups heavy cream
07 - ½ cup whole milk
08 - 3 tbsp unsalted butter
→ Seasonings
09 - ½ tsp dried thyme
10 - ½ tsp ground black pepper
11 - ½ tsp salt, plus more to taste
12 - ¼ tsp ground nutmeg
→ Optional Additions
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. Generously 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 pinch of salt. Cook, stirring frequently, until deeply golden and caramelized, 20-25 minutes. Add minced garlic during final minute. Remove from heat.
03 - Combine heavy cream, whole milk, thyme, nutmeg, black pepper, and remaining 1 tbsp butter in a small saucepan. Heat over medium-low until steaming, avoiding boiling. If using flour, whisk until smooth and slightly thickened.
04 - Arrange half the sweet potato slices in overlapping rows in the prepared dish. Season lightly with salt.
05 - Spread half the caramelized onions over potatoes. Sprinkle with half the Gruyère and half the cheddar cheese.
06 - Layer remaining sweet potatoes, followed by remaining onions and cheeses.
07 - Pour warm cream mixture evenly over the layered ingredients, ensuring coverage across the dish.
08 - Cover tightly with aluminum foil. Bake for 40 minutes until potatoes begin to soften.
09 - Remove foil and continue baking 20 minutes until top is golden brown and potatoes are fork-tender.
10 - Let gratin rest 10 minutes before serving to allow layers to set. Garnish with fresh chives if desired.
# Expert Suggestions:
01 -
- The way the natural sweetness of the potatoes plays against the sharp cheddar and nutty Gruyère is absolutely magical
- Caramelized onions take this from ordinary side dish to something people actually ask for by name
02 -
- Use a mandoline if you have one because consistently thin potatoes make all the difference
- The cream mixture should be hot when you pour it so it starts working immediately
03 -
- Sprinkle some smoked paprika over the top during the last 10 minutes for a subtle smoky note
- Place a baking sheet on the rack below to catch any bubbling over