Cheesy Sweet Potato Gratin (Printable Version)
Layered sweet potatoes with caramelized onions and a blend of melted cheeses baked until golden.
# 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 Enhancements
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 during the last minute and remove from heat.
03 - In a small saucepan over medium-low heat, combine heavy cream, whole milk, dried thyme, ground nutmeg, black pepper, and remaining 1 tbsp butter. 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 evenly 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 - Carefully pour the warm cream mixture evenly over the layered ingredients, ensuring coverage across the entire dish.
08 - Cover baking dish tightly with aluminum foil. Bake for 40 minutes until potatoes begin to soften.
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 gratin rest for 10 minutes before serving to allow layers to set. Garnish with chopped fresh chives if desired.
# Expert Tips:
01 -
- The way the cream bubbles up between the layers, creating those irresistible golden edges that everyone fights over
- How the onions slowly melt into something sweet and savory, almost like a built-in jam
- That moment when you pull it from the oven and the whole kitchen smells like butter and comfort
02 -
- A mandoline is your friend here because hand-slicing sweet potatoes thin enough and evenly enough is genuinely frustrating
- The onions need time and patience, so do not crank the heat to high or they will scorch instead of caramelize
- Covering the dish for the first 40 minutes is non-negotiable or the potatoes will still be hard when the cheese is burning
03 -
- Sprinkle a little extra cheese on top before the final 20 minutes if you want an even more impressive crust
- Letting it rest those 10 minutes seems like torture but it really does make serving easier