Cheesy Sweet Potato Gratin (Printable)
Comforting gratin of sweet potatoes layered with caramelized onions and cheese, baked until golden and tender.
# What You 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 minced garlic and cook for 1 minute more. Remove from heat.
03 - In a small saucepan, combine heavy cream, whole milk, thyme, nutmeg, black pepper, and remaining 1 tbsp butter. Heat over medium-low heat until steaming but not boiling. If using flour, whisk it in until smooth and slightly thickened.
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 potatoes, caramelized onions, and cheeses, creating another complete layer.
07 - Pour the warm cream mixture evenly over the entire dish, ensuring it distributes through all layers.
08 - Cover the baking dish tightly with aluminum foil. Bake for 40 minutes.
09 - Remove the foil and continue baking uncovered for an additional 20 minutes, or until the top is golden brown and potatoes are fork-tender.
10 - Allow the gratin to rest for 10 minutes before serving to let the layers set. Garnish with fresh chives if desired.
# Expert Tips:
01 -
- The sweet and savory combo hits every comfort button
- It makes you look like you spent hours when really the oven does the work
- Leftovers reheat beautifully for lunch the next day
02 -
- Rushing the caramelization step is the biggest mistake you can make, those onions need time to develop their sweetness
- Letting the gratin rest before cutting seems impossible but makes all the difference between a messy scoop and neat servings
03 -
- Use a mandoline for paper thin, even slices that cook at the same rate
- Grate your own cheese instead of buying pre shredded, it melts so much better