Cheesy Sweet Potato Gratin (Printable)
Layers of sweet potatoes and onions baked with melted cheeses for a rich, comforting dish.
# 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 gluten-free flour (or all-purpose flour) for thickening
14 - 2 tbsp chopped fresh chives for garnish
# Directions:
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 (do not boil). If using flour, whisk it in until smooth to slightly thicken.
04 - Layer half of the sweet potato slices in 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 cheddar cheese.
06 - Repeat with remaining potatoes, onions, and cheeses.
07 - Pour the warm cream mixture evenly over the layered ingredients.
08 - Cover tightly with foil and bake for 40 minutes.
09 - Remove foil and bake uncovered for an additional 20 minutes, or until the top is golden and the potatoes are fork-tender.
10 - Let rest 10 minutes before serving. Garnish with fresh chives if desired.
# Expert Advice:
01 -
- The slow-caramelized onions become sweet and savory, balancing the natural sweetness of the potatoes in a way that feels almost accidental
- This dish travels beautifully and tastes even better after resting, making it perfect for potlucks and dinner parties
02 -
- Onion caramelization cannot be rushed. Low and slow gives you sweetness; high and fast gives you burned bits and bitterness.
- Thick potato slices will not cook through, while paper-thin ones will disappear. Aim for about an eighth of an inch.
03 -
- Slide a knife into the center after the foil comes off to check potato tenderness. If it meets resistance, recover and bake longer.
- Place the baking dish on a lined sheet pan to catch any bubbly overflow in your oven.